| Compensation and Retirement Disclosure [Abstract] | Period [Axis] |
|---|
2016-01-01 - 2016-12-31 |
|---|
Compensation and Retirement Disclosure [Abstract] | |
Schedule of Changes in the Projected Benefit Obligation and Plan Assets of the Corporation’s Pension and Postretirement Plans | The following schedule sets forth the changes in the projected benefit obligation and plan assets of the Corporation's Pension and Postretirement Plans: | | | | | | | | | | | | | | | | | | | | Pension Plan | | Postretirement Plan | (Dollars in thousands) | | 2016 | | 2015 | | 2016 | | 2015 | Projected benefit obligation: | | | | | | | | | Benefit obligation at beginning of year | | $ | 119,873 |
| | $ | 129,160 |
| | $ | 3,247 |
| | $ | 3,702 |
| Service cost | | 1,041 |
| | 1,021 |
| | 9 |
| | 16 |
| Interest cost | | 5,335 |
| | 5,242 |
| | 132 |
| | 133 |
| Net actuarial loss (gain) | | 2,684 |
| | (10,837 | ) | | (478 | ) | | (363 | ) | Benefits paid | | (4,965 | ) | | (4,713 | ) | | (309 | ) | | (241 | ) | Benefit obligation at end of year | | 123,968 |
| | 119,873 |
| | 2,601 |
| | 3,247 |
| Fair value of plan assets: | | | | | | | | | Fair value of plan assets at beginning of year | | 126,930 |
| | 130,775 |
| | — |
| | — |
| Actual return on plan assets | | 10,786 |
| | 868 |
| | — |
| | — |
| Employer contributions | | — |
| | — |
| | 309 |
| | 241 |
| Benefits paid | | (4,965 | ) | | (4,713 | ) | | (309 | ) | | (241 | ) | Fair value of plan assets at end of year | | 132,751 |
| | 126,930 |
| | — |
| | — |
| Funded (unfunded) status at December 31 | | $ | 8,783 |
| | $ | 7,057 |
| | $ | (2,601 | ) | | $ | (3,247 | ) | Accumulated benefit obligation | | $ | 115,418 |
| | $ | 109,583 |
| | $ | 2,601 |
| | $ | 3,247 |
|
|
Schedule of Weighted-average rate assumptions of the Pension and Postretirement Plans | Weighted-average rate assumptions of the Pension and Postretirement Plans follow: | | | | | | | | | | | | | | | | | | | | | | Pension Plan | | Postretirement Plan | | | 2016 | | 2015 | | 2014 | | 2016 | | 2015 | | 2014 | Discount rate used in determining benefit obligation — December 31 | | 4.22 | % | | 4.55 | % | | 4.15 | % | | 3.79 | % | | 4.23 | % | | 3.75 | % | Discount rate used in determining expense | | 4.55 |
| | 4.15 |
| | 5.00 |
| | 4.23 |
| | 3.75 |
| | 4.27 |
| Expected long-term return on Pension Plan assets | | 6.75 |
| | 6.75 |
| | 7.00 |
| | — |
| | — |
| | — |
| Rate of compensation increase used in determining benefit obligation — December 31 | | 3.50 |
| | 3.50 |
| | 3.50 |
| | — |
| | — |
| | — |
| Rate of compensation increase used in determining pension expense | | 3.50 |
| | 3.50 |
| | 3.50 |
| | — |
| | — |
| | — |
| Year 1 increase in cost of postretirement benefits | | — |
| | — |
| | — |
| | 7.0 |
| | 7.5 |
| | 8.0 |
|
|
Schedule of Net periodic Pension Cost (Income) of the Pension and Postretirement Plans | Net periodic pension cost (income) of the Pension and Postretirement Plans was as follows for the years ended December 31: | | | | | | | | | | | | | | | | | | | | | | | | | | | | Pension Plan | | Postretirement Plan | (Dollars in thousands) | | 2016 | | 2015 | | 2014 | | 2016 | | 2015 | | 2014 | Service cost | | $ | 1,041 |
| | $ | 1,021 |
| | $ | 944 |
| | $ | 9 |
| | $ | 16 |
| | $ | 18 |
| Interest cost | | 5,335 |
| | 5,242 |
| | 5,167 |
| | 132 |
| | 133 |
| | 142 |
| Expected return on plan assets | | (8,562 | ) | | (8,645 | ) | | (8,314 | ) | | — |
| | — |
| | — |
| Amortization of prior service credit | | — |
| | (5 | ) | | (1 | ) | | 117 |
| | 130 |
| | 130 |
| Amortization of net actuarial loss (gain) | | 2,259 |
| | 3,962 |
| | 2,159 |
| | (100 | ) | | (1 | ) | | (104 | ) | Net cost (income) | | $ | 73 |
| | $ | 1,575 |
| | $ | (45 | ) | | $ | 158 |
| | $ | 278 |
| | $ | 186 |
|
|
Schedule of Estimated Future Benefit Payments Under the Pension and Postretirement Plans | The following schedule presents estimated future benefit payments for the next 10 years under the Pension and Postretirement Plans for retirees already receiving benefits and future retirees, assuming they retire and begin receiving unreduced benefits as soon as they are eligible: | | | | | | | | | | (Dollars in thousands) | | Pension Plan | | Postretirement Plan | 2017 | | $ | 5,474 |
| | $ | 243 |
| 2018 | | 5,706 |
| | 239 |
| 2019 | | 6,083 |
| | 240 |
| 2020 | | 6,263 |
| | 237 |
| 2021 | | 6,626 |
| | 234 |
| 2022 - 2026 | | 36,438 |
| | 1,028 |
| Total | | $ | 66,590 |
| | $ | 2,221 |
|
|
Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates | A one percentage-point change in these rates would have the following effects: | | | | | | | | | | | | One Percentage-Point | (Dollars in thousands) | | Increase | | Decrease | Effect on total of service and interest cost components in 2016 | | $ | 14 |
| | $ | (13 | ) | Effect on postretirement benefit obligation as of December 31, 2016 | | 204 |
| | (194 | ) |
|
Schedule of Allocation of Plan Assets | The Pension Plan's asset allocation by asset category was as follows: | | | | | | | | | | December 31, | Asset Category | | 2016 | | 2015 | Equity securities | | 69 | % | | 68 | % | Debt securities | | 29 |
| | 31 |
| Other | | 2 |
| | 1 |
| Total | | 100 | % | | 100 | % |
The following schedule sets forth the fair value of the Pension Plan's assets and the level of the valuation inputs used to value those assets at December 31, 2016 and 2015: | | | | | | | | | | | | | | | | | | (Dollars in thousands) | | Quoted Prices In Active Markets for Identical Assets (Level 1) | | Significant Other Observable Inputs (Level 2) | | Significant Unobservable Inputs (Level 3) | | Total | December 31, 2016 | | | | | | | | | Cash | | $ | 2,825 |
| | $ | — |
| | $ | — |
| | $ | 2,825 |
| Equity securities: | |
| |
| |
| |
| U.S. large- and mid-cap stocks(1) | | 55,389 |
| | — |
| | — |
| | 55,389 |
| U.S. small-cap mutual funds | | 5,687 |
| | — |
| | — |
| | 5,687 |
| International large-cap mutual funds | | 13,701 |
| | — |
| | — |
| | 13,701 |
| Emerging markets mutual funds | | 5,147 |
| | — |
| | — |
| | 5,147 |
| Chemical Financial Corporation common stock | | 11,412 |
| | — |
| | — |
| | 11,412 |
| Debt securities: | |
| |
| |
| |
| U.S. Treasury and government sponsored agency bonds and notes | | — |
| | 806 |
| | — |
| | 806 |
| Corporate bonds(2) | | — |
| | 1,503 |
| | — |
| | 1,503 |
| Mutual funds(3) | | 36,220 |
| | — |
| | — |
| | 36,220 |
| Other | | 61 |
| | — |
| | — |
| | 61 |
| Total | | $ | 130,442 |
| | $ | 2,309 |
| | $ | — |
| | $ | 132,751 |
| December 31, 2015 | | | | | | | | | Cash | | $ | 354 |
| | $ | — |
| | $ | — |
| | $ | 354 |
| Equity securities: | | | | | | | | | U.S. large- and mid-cap stocks(1) | | 55,709 |
| | — |
| | — |
| | 55,709 |
| U.S. small-cap mutual funds | | 4,749 |
| | — |
| | — |
| | 4,749 |
| International large-cap mutual funds | | 14,124 |
| | — |
| | — |
| | 14,124 |
| Emerging markets mutual funds | | 4,886 |
| | — |
| | — |
| | 4,886 |
| Chemical Financial Corporation common stock | | 7,219 |
| | — |
| | — |
| | 7,219 |
| Debt securities: | | | | | | | | | U.S. Treasury and government sponsored agency bonds and notes | | — |
| | 2,815 |
| | — |
| | 2,815 |
| Corporate bonds(2) | | — |
| | 3,554 |
| | — |
| | 3,554 |
| Mutual funds(3) | | 33,424 |
| | — |
| | — |
| | 33,424 |
| Other | | 96 |
| | — |
| | — |
| | 96 |
| Total | | $ | 120,561 |
| | $ | 6,369 |
| | $ | — |
| | $ | 126,930 |
|
| | (1) | Comprised of common stocks and mutual funds traded on U.S. Exchanges whose issuers had market capitalizations exceeding $3 billion. |
| | (2) | Comprised of investment grade bonds of U.S. issuers from diverse industries. |
| | (3) | Comprised primarily of fixed-income bonds issued by the U.S. Treasury and government sponsored agencies and bonds of U.S. and foreign issuers from diverse industries. |
|
Schedule of Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax, Related to the Corporation’s Pension, Postretirement and Supplemental Plans | The following sets forth the changes in accumulated other comprehensive income (loss), net of tax, related to the Corporation's Pension, Postretirement and Supplemental Plans during 2016: | | | | | | | | | | | | | | | | | | (Dollars in thousands) | | Pension Plan | | Postretirement Plan | | Supplemental Plan | | Total | Accumulated other comprehensive income (loss) at beginning of year | | $ | (27,291 | ) | | $ | 402 |
| | $ | (255 | ) | | $ | (27,144 | ) | Comprehensive income (loss) adjustment: | |
| |
| |
| | | Prior service costs (credits) | | — |
| | 76 |
| | — |
| | 76 |
| Net actuarial (income) loss | | 1,168 |
| | 246 |
| | (240 | ) | | 1,174 |
| Comprehensive income (loss) adjustment | | 1,168 |
| | 322 |
| | (240 | ) | | 1,250 |
| Accumulated other comprehensive income (loss) at end of year | | $ | (26,123 | ) | | $ | 724 |
| | $ | (495 | ) | | $ | (25,894 | ) |
|
Schedule of Estimated Income (Loss) That Will Be Amortized From Accumulated Other Comprehensive Income (Loss) Into Net Periodic Cost | The estimated income (loss) that will be amortized from accumulated other comprehensive income (loss) into net periodic cost, net of tax, in 2017 is as follows: | | | | | | | | | | | | | | | | | | (Dollars in thousands) | | Pension Plan | | Postretirement Plan | | Supplemental Plan | | Total | Prior service (costs) credits | | $ | — |
| | $ | — |
| | $ | — |
| | $ | — |
| Net gain (loss) | | (1,436 | ) | | 105 |
| | (67 | ) | | (1,398 | ) | Total | | $ | (1,436 | ) | | $ | 105 |
| | $ | (67 | ) | | $ | (1,398 | ) |
|