Regulatory Capital and Reserve Requirements (Details) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum average regulatory cash reserve balance	$ 46,300,000	$ 29,300,000
Chemical Financial Corporation [Member]
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Cash dividends paid to parent company	(64,468,000)	(24,488,000)	(27,550,000)
Risk weighted assets	5,700,000,000	4,640,000,000
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	705,130,000	649,836,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	456,302,000	371,465,000
Actual, Ratio	12.40%	14.00%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	633,779,000	591,535,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	228,151,000	185,732,000
Actual, Ratio	11.10%	12.70%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Leverage Ratio:
Actual, Capital Amount	633,779,000	591,535,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	273,226,000	239,010,000
Actual, Ratio	9.30%	9.90%
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	64,500,000	24,500,000	27,600,000
Risk weighted assets	5,700,000,000	4,640,000,000
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	654,031,000	579,494,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	455,633,000	370,881,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	569,541,000	463,601,000
Actual, Ratio	11.50%	12.50%
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	582,783,000	521,283,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	227,816,000	185,440,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	341,725,000	278,160,000
Actual, Ratio	10.20%	11.20%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	6.00%	6.00%
Leverage Ratio:
Actual, Capital Amount	582,783,000	521,283,000
Minimum Required for Capital Adequacy Purposes, Capital Amount	273,048,000	238,884,000
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 341,310,000	$ 298,605,000
Actual, Ratio	8.50%	8.70%
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%