Regulatory Capital and Reserve Requirements (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum average regulatory cash reserve balance	$ 65,300	$ 46,300
Chemical Financial Corporation [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends paid to parent company	(56,860)	(64,468)	$ (24,488)
Risk weighted assets	7,140,000	5,700,000
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	841,257	705,130
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 571,509	$ 456,302
Actual, Ratio	11.80%	12.40%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 767,929	$ 633,779
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 428,631	$ 228,151
Actual, Ratio	10.70%	11.10%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	4.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets [Abstract]
Actual, Capital Amount	$ 753,815
Minimum Required for Capital Adequacy Purposes, Capital Amount	10.60%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 321,474
Actual, Ratio	4.50%
Leverage Ratio:
Actual, Capital Amount	$ 767,929	$ 633,779
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 356,396	$ 273,226
Actual, Ratio	8.60%	9.30%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Chemical Bank [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends paid to parent company	$ 56,900	$ 64,500	$ 24,500
Risk weighted assets	7,130,000	5,700,000
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	830,294	654,031
Minimum Required for Capital Adequacy Purposes, Capital Amount	570,073	455,633
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 712,591	$ 569,541
Actual, Ratio	11.70%	11.50%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 756,966	$ 582,783
Minimum Required for Capital Adequacy Purposes, Capital Amount	427,555	227,816
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 570,073	$ 341,725
Actual, Ratio	10.60%	10.20%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	8.00%	6.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets [Abstract]
Actual, Capital Amount	$ 756,966
Minimum Required for Capital Adequacy Purposes, Capital Amount	10.60%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 320,666
Actual, Ratio	4.50%
Minimum Required for Capital Adequacy Purposes, Ratio	$ 463,184
Required to be Well Capital Under Prompt Corrective Action Regulations, Ratio	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 756,966	$ 582,783
Minimum Required for Capital Adequacy Purposes, Capital Amount	355,911	273,048
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 444,888	$ 341,310
Actual, Ratio	8.50%	8.50%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	5.00%	5.00%