| Component: (Network and Table) | |
|---|---|
| Network | 2416404 - Disclosure - Retirement Plans (Weighted-average rate assumptions of the Pension and Postretirement Plans) (Details) (http://www.chemicalbankmi.com/role/RetirementPlansWeightedAverageRateAssumptionsOfPensionAndPostretirementPlansDetails) |
| Table | Defined Benefit Plans and Other Postretirement Benefit Plans Disclosures [Table] |
| Reporting Entity [Axis] | 0000019612 (http://www.sec.gov/CIK) |
| Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] | Period [Axis] | |||||
|---|---|---|---|---|---|---|
2016-01-01 - 2016-12-31 | 2015-01-01 - 2015-12-31 | 2014-01-01 - 2014-12-31 | ||||
| Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] | Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] | Defined Benefit Plans and Other Postretirement Benefit Plans [Axis] | ||||
| Pension Plan | Postretirement Plan | Pension Plan | Postretirement Plan | Pension Plan | Postretirement Plan | |
Discount rate used in determining benefit obligation — December 31 | 4.22% | 3.79% | 4.55% | 4.23% | 4.15% | 3.75% |
Discount rate used in determining expense | 4.55% | 4.23% | 4.15% | 3.75% | 5.00% | 4.27% |
Expected long-term return on Pension Plan assets | ||||||
Rate of compensation increase used in determining benefit obligation — December 31 | ||||||
Rate of compensation increase used in determining pension expense | ||||||
Year 1 increase in cost of postretirement benefits | ||||||