Regulatory Capital (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk weighted assets	$ 7,220,000	$ 7,140,000	$ 5,580,000
Chemical Financial Corporation [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	832,457	841,257	727,090
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 577,668	$ 571,509	$ 446,173
Actual, Ratio	11.50%	11.80%	13.00%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 762,139	$ 767,929	$ 657,307
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 433,251	$ 428,631	$ 334,630
Actual, Ratio	10.60%	10.70%	11.80%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	6.00%	6.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 762,139	$ 753,815	$ 657,307
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 324,938	$ 321,474	$ 250,972
Actual, Ratio	10.60%	10.60%	11.80%
Minimum Required for Capital Adequacy Purposes, Ratio	4.50%	4.50%	4.50%
Leverage Ratio:
Actual, Capital Amount	$ 762,139	$ 767,929	$ 657,307
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 357,773	$ 356,396	$ 289,948
Actual, Ratio	8.50%	8.60%	9.10%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Chemical Bank [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 840,372	$ 830,294	$ 676,488
Minimum Required for Capital Adequacy Purposes, Capital Amount	576,068	570,073	445,471
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 720,086	$ 712,591	$ 556,838
Actual, Ratio	11.70%	11.70%	12.10%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	10.00%	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 770,054	$ 756,966	$ 606,813
Minimum Required for Capital Adequacy Purposes, Capital Amount	432,051	427,555	334,103
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 576,068	$ 570,073	$ 445,471
Actual, Ratio	10.70%	10.60%	10.90%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	6.00%	6.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	8.00%	8.00%	8.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 770,054	$ 756,966	$ 606,813
Minimum Required for Capital Adequacy Purposes, Capital Amount	324,038	320,666	250,577
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 468,056	$ 463,184	$ 361,945
Actual, Ratio	10.70%	10.60%	10.90%
Minimum Required for Capital Adequacy Purposes, Ratio	4.50%	4.50%	4.50%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	6.50%	6.50%	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 770,054	$ 756,966	$ 606,813
Minimum Required for Capital Adequacy Purposes, Capital Amount	357,190	355,911	289,840
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 446,488	$ 444,888	$ 362,300
Actual, Ratio	8.60%	8.50%	8.40%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	5.00%	5.00%	5.00%