| Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] | Period [Axis] |
|---|
2016-01-01 - 2016-12-31 |
|---|
Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Abstract] | |
Schedule of Defined Benefit Plans Disclosures | The following table sets forth reconciliations of plan assets and the projected benefit obligation, the weighted-average assumptions used to determine year-end benefit obligations, and the amounts recognized in accumulated other comprehensive income (loss) for the Corporation’s defined benefit pension plans and postretirement benefit plan at December 31, 2016 and 2015. The Corporation used a measurement date of December 31, 2016 for these plans. | | | | | | | | | | | | | | | | | | | | | | | | | | | | Defined Benefit Pension Plans | | | | | | Qualified | | | Non-Qualified | | Postretirement Benefit Plan | (dollar amounts in millions) | 2016 | | 2015 | | 2016 | | 2015 | | 2016 | | 2015 | Change in fair value of plan assets: | | | | | | | | | | | | | | Fair value of plan assets at January 1 | $ | 2,346 |
| | | $ | 2,541 |
| | | $ | — |
| | $ | — |
| | $ | 61 |
| | $ | 67 |
| Actual return on plan assets | 200 |
| | | (73 | ) | | | — |
| | — |
| | 2 |
| | — |
| Employer contributions | — |
| | | — |
| | | — |
| | — |
| | 4 |
| | — |
| Benefits paid | (93 | ) | | | (122 | ) | (a) | | — |
| | — |
| | (5 | ) | | (6 | ) | Fair value of plan assets at December 31 | $ | 2,453 |
| | | $ | 2,346 |
| | | $ | — |
| | $ | — |
| | $ | 62 |
| | $ | 61 |
| Change in projected benefit obligation: | | | | | | | | | | | | | | Projected benefit obligation at January 1 | $ | 1,916 |
| | | $ | 2,070 |
| | | $ | 222 |
| | $ | 235 |
| | $ | 59 |
| | $ | 73 |
| Service cost | 31 |
| | | 35 |
| | | 3 |
| | 4 |
| | — |
| | — |
| Interest cost | 87 |
| | | 88 |
| | | 10 |
| | 10 |
| | 3 |
| | 3 |
| Actuarial loss (gain) | 161 |
| | | (155 | ) | | | 11 |
| | (16 | ) | | (2 | ) | | (8 | ) | Benefits paid | (93 | ) | | | (122 | ) | (a) | | (11 | ) | | (11 | ) | | (5 | ) | | (6 | ) | Plan change | (200 | ) | | | — |
| | | (34 | ) | | — |
| | — |
| | (3 | ) | Projected benefit obligation at December 31 | $ | 1,902 |
| | | $ | 1,916 |
| | | $ | 201 |
| | $ | 222 |
| | $ | 55 |
| | $ | 59 |
| Accumulated benefit obligation | $ | 1,894 |
| | | $ | 1,756 |
| | | $ | 198 |
| | $ | 191 |
| | $ | 55 |
| | $ | 59 |
| Funded status at December 31 (b) (c) | $ | 551 |
| | | $ | 430 |
| | | $ | (201 | ) | | $ | (222 | ) | | $ | 7 |
| | $ | 2 |
| Weighted-average assumptions used: | | | | | | | | | | | | | | Discount rate | 4.23 | % | | | 4.82 | % | | | 4.23 | % | | 4.82 | % | | 3.92 | % | | 4.53 | % | Rate of compensation increase | 3.50 |
| | | 3.75 |
| | | 3.50 |
| | 3.75 |
| | n/a |
| | n/a |
| Healthcare cost trend rate: | | | | | | | | | | | | | | Cost trend rate assumed for next year | n/a |
| | | n/a |
| | | n/a |
| | n/a |
| | 6.50 |
| | 7.00 |
| Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) | n/a |
| | | n/a |
| | | n/a |
| | n/a |
| | 5.00 |
| | 5.00 |
| Year when rate reaches the ultimate trend rate | n/a |
| | | n/a |
| | | n/a |
| | n/a |
| | 2027 |
| | 2027 |
| Amounts recognized in accumulated other comprehensive income (loss) before income taxes: | | | | | | | | | | | | | | Net actuarial loss | $ | (673 | ) | | | $ | (586 | ) | | | $ | (82 | ) | | $ | (78 | ) | | $ | (20 | ) | | $ | (22 | ) | Prior service credit (cost) | 178 |
| | | (21 | ) | | | 50 |
| | 21 |
| | 1 |
| | 1 |
| Balance at December 31 | $ | (495 | ) | | | $ | (607 | ) | | | $ | (32 | ) | | $ | (57 | ) | | $ | (19 | ) | | $ | (21 | ) |
| | (a) | Included $56 million in benefit payments made to certain terminated vested eligible participants who elected to receive lump-sum settlements in 2015. |
| | (b) | Based on projected benefit obligation for defined benefit pension plans and accumulated benefit obligation for postretirement benefit plan. |
| | (c) | The Corporation recognizes the overfunded and underfunded status of the plans in “accrued income and other assets” and “accrued expenses and other liabilities,” respectively, on the consolidated balance sheets. |
n/a - not applicable |
Changes in Plan Assets and Benefit Obligations Recognized in Other Comprehensive Income (Loss) | The following table details the changes in plan assets and benefit obligations recognized in other comprehensive income (loss) for the year ended December 31, 2016. | | | | | | | | | | | | | | | | | | Defined Benefit Pension Plans | | | | | (in millions) | Qualified | | Non-Qualified | | Postretirement Benefit Plan | | Total | Actuarial (loss) gain arising during the period | $ | (124 | ) | | $ | (11 | ) | | $ | 1 |
| | $ | (134 | ) | Prior service credit arising during the period | 200 |
| | 34 |
| | — |
| | 234 |
| Amortization of net actuarial loss | 38 |
| | 7 |
| | 1 |
| | 46 |
| Amortization of prior service credit | (2 | ) | | (5 | ) | | — |
| | (7 | ) | Total recognized in other comprehensive income | $ | 112 |
| | $ | 25 |
| | $ | 2 |
| | $ | 139 |
|
|
Components of Net Periodic Defined Benefit Cost | Components of net periodic defined benefit cost and postretirement benefit cost, the actual return on plan assets and the weighted-average assumptions used were as follows. | | | | | | | | | | | | | | | | | | | | | | | | | | Defined Benefit Pension Plans | (dollar amounts in millions) | Qualified | | Non-Qualified | Years Ended December 31 | 2016 | | 2015 | | 2014 | | 2016 | | 2015 | | 2014 | Service cost | $ | 31 |
| | $ | 35 |
| | $ | 29 |
| | $ | 3 |
| | $ | 4 |
| | $ | 3 |
| Interest cost | 87 |
| | 88 |
| | 88 |
| | 10 |
| | 10 |
| | 10 |
| Expected return on plan assets | (163 | ) | | (159 | ) | | (131 | ) | | — |
| | — |
| | — |
| Amortization of prior service (credit) cost | (2 | ) | | 4 |
| | 6 |
| | (5 | ) | | (4 | ) | | (4 | ) | Amortization of net loss | 38 |
| | 59 |
| | 31 |
| | 7 |
| | 10 |
| | 7 |
| Net periodic defined benefit (credit) cost | $ | (9 | ) | | $ | 27 |
| | $ | 23 |
| | $ | 15 |
| | $ | 20 |
| | $ | 16 |
| Actual return on plan assets | $ | 200 |
| | $ | (73 | ) | | $ | 278 |
| | n/a |
| | n/a |
| | n/a |
| Actual rate of return on plan assets | 8.66 | % | | (2.95 | )% | | 13.88 | % | | n/a |
| | n/a |
| | n/a |
| Weighted-average assumptions used: | | | | | | | | | | | | Discount rate | 4.53 | % | | 4.28 | % | | 5.17 | % | | 4.53 | % | | 4.28 | % | | 5.17 | % | Expected long-term return on plan assets | 6.75 |
| | 6.75 |
| | 6.75 |
| | n/a |
| | n/a |
| | n/a |
| Rate of compensation increase | 3.75 |
| | 3.75 |
| | 4.00 |
| | 3.75 |
| | 3.75 |
| | 4.00 |
|
n/a - not applicable | | | | | | | | | | | | | (dollar amounts in millions) | Postretirement Benefit Plan | Years Ended December 31 | 2016 | | 2015 | | 2014 | Interest cost | $ | 3 |
| | $ | 3 |
| | $ | 3 |
| Expected return on plan assets | (4 | ) | | (4 | ) | | (4 | ) | Amortization of prior service cost | — |
| | 1 |
| | 1 |
| Amortization of net loss | 1 |
| | 1 |
| | 1 |
| Net periodic postretirement benefit cost | $ | — |
| | $ | 1 |
| | $ | 1 |
| Actual return on plan assets | $ | 2 |
| | $ | — |
| | $ | 3 |
| Actual rate of return on plan assets | 2.83 | % | | (0.53 | )% | | 4.62 | % | Weighted-average assumptions used: | | | | | | Discount rate | 4.53 | % | | 3.99 | % | | 4.59 | % | Expected long-term return on plan assets | 5.00 |
| | 5.00 |
| | 5.00 |
| Healthcare cost trend rate: | | | | | | Cost trend rate assumed | 7.00 |
| | 7.00 |
| | 7.50 |
| Rate to which the cost trend rate is assumed to decline (the ultimate trend rate) | 5.00 |
| | 5.00 |
| | 5.00 |
| Year that the rate reaches the ultimate trend rate | 2027 |
| | 2026 |
| | 2033 |
|
|
Balances Remaining in Accumulated Other Comprehensive Income (Loss) to be Recognized over Next Fiscal Year | The estimated portion of balances remaining in accumulated other comprehensive income (loss) that are expected to be recognized as a component of net periodic benefit cost in the year ended December 31, 2017 are as follows. | | | | | | | | | | | | | | | | | | Defined Benefit Pension Plans | | | | | (in millions) | Qualified | | Non-Qualified | | Postretirement Benefit Plan | | Total | Net loss | $ | 43 |
| | $ | 8 |
| | $ | 1 |
| | $ | 52 |
| Prior service credit | (19 | ) | | (8 | ) | | — |
| | (27 | ) |
|
Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates | Assumed healthcare cost trend rates have a significant effect on the amounts reported for the postretirement benefit plan. A one-percentage-point change in 2016 assumed healthcare and prescription drug cost trend rates would have the following effects. | | | | | | | | | | One-Percentage-Point | (in millions) | Increase | | Decrease | Effect on postretirement benefit obligation | $ | 3 |
| | $ | (3 | ) | Effect on total service and interest cost | — |
| | — |
|
|
Fair Value of Defined Benefit Plan Investments | The fair values of the Corporation’s qualified defined benefit pension plan investments measured at fair value on a recurring basis at December 31, 2016 and 2015, by asset category and level within the fair value hierarchy, are detailed in the table below. | | | | | | | | | | | | | | | | | (in millions) | Total | | Level 1 | | Level 2 | | Level 3 | December 31, 2016 | | | | | | | | Cash equivalent securities: | | | | | | | | Commercial paper | $ | 2 |
| | $ | — |
| | $ | 2 |
| | $ | — |
| Common stock | 850 |
| | 850 |
| | — |
| | — |
| Fixed income securities: | | | | | | | | U.S. Treasury and other U.S. government agency securities | 377 |
| | 377 |
| | — |
| | — |
| Corporate and municipal bonds and notes | 709 |
| | — |
| | 709 |
| | — |
| Collateralized mortgage obligations | 15 |
| | — |
| | 15 |
| | — |
| U.S. government agency mortgage-backed securities | 8 |
| | — |
| | 8 |
| | — |
| Private placements | 71 |
| | — |
| | — |
| | 71 |
| Total investments in the fair value hierarchy | 2,032 |
|
| 1,227 |
|
| 734 |
|
| 71 |
| | | | | | | | | Investments measured at net asset value: | | | | | | | | Collective investment funds | 416 |
| |
|
| |
|
| |
|
| Total investments at fair value | $ | 2,448 |
| |
|
| |
|
| |
|
| December 31, 2015 | | | | | | | | Cash equivalent securities: | | | | | | | | Mutual funds | $ | 43 |
| | $ | 43 |
| | $ | — |
| | $ | — |
| Equity securities: | | | | | | | | Mutual funds | 69 |
| | 69 |
| | — |
| | — |
| Common stock | 480 |
| | 478 |
| | 2 |
| | — |
| Fixed income securities: | | | | | | | | U.S. Treasury and other U.S. government agency securities | 368 |
| | 368 |
| | — |
| | — |
| Corporate and municipal bonds and notes | 729 |
| | — |
| | 729 |
| | — |
| Collateralized mortgage obligations | 18 |
| | — |
| | 18 |
| | — |
| U.S. government agency mortgage-backed securities | 8 |
| | — |
| | 8 |
| | — |
| Private placements | 105 |
| | — |
| | — |
| | 105 |
| Total investments in the fair value hierarchy | 1,820 |
| | 958 |
| | 757 |
| | 105 |
| | | | | | | | | Investments measured at net asset value: | | | | | | | | Collective investment funds | 527 |
| | | | | | | Total investments at fair value | $ | 2,347 |
| | | | | | |
|
Changes in Level 3 Defined Benefit Plan Investments | The table below provides a summary of changes in the Corporation’s qualified defined benefit pension plan’s Level 3 investments measured at fair value on a recurring basis for the years ended December 31, 2016 and 2015. | | | | | | | | | | | | | | | | | | | | | | | | | | Balance at Beginning of Period | | | | | | | | | | Balance at End of Period | | | Net Gains (Losses) | | | | | | (in millions) | | Realized | | Unrealized | | Purchases | | Sales | | Year Ended December 31, 2016 | | | | | | | | | | | | Private placements | $ | 105 |
| | $ | 1 |
| | $ | 3 |
| | $ | 64 |
| | $ | (102 | ) | | $ | 71 |
| Year Ended December 31, 2015 | | | | | | | | | | | | Private placements | $ | 73 |
| | $ | — |
| | $ | (5 | ) | | $ | 108 |
| | $ | (71 | ) | | $ | 105 |
|
|
Estimated Future Benefit Payments | The Corporation currently expects to make no employer contributions to the qualified and non-qualified defined benefit pension plans and postretirement benefit plan for the year ended December 31, 2017. | | | | | | | | | | | | | | Estimated Future Benefit Payments | (in millions) Years Ended December 31 | Qualified Defined Benefit Pension Plan | | Non-Qualified Defined Benefit Pension Plan | | Postretirement Benefit Plan (a) | 2017 | $ | 120 |
| | $ | 11 |
| | $ | 6 |
| 2018 | 119 |
| | 12 |
| | 6 |
| 2019 | 124 |
| | 12 |
| | 6 |
| 2020 | 126 |
| | 13 |
| | 5 |
| 2021 | 129 |
| | 13 |
| | 5 |
| 2022 - 2026 | 657 |
| | 65 |
| | 21 |
|
| | (a) | Estimated benefit payments in the postretirement benefit plan are net of estimated Medicare subsidies. |
|
