Regulatory Capital (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014	Sep. 30, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk weighted assets	$ 7,100,000	$ 5,700,000	$ 5,060,000
Chemical Financial Corporation [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	825,649	705,130	760,324
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 569,695	$ 456,302	$ 404,420
Actual, Ratio	11.60%	12.40%	15.00%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 750,023	$ 633,779	$ 696,963
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 427,272	$ 228,151	$ 202,210
Actual, Ratio	10.50%	11.10%	13.80%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	4.00%	4.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 736,158
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 320,454
Actual, Ratio	10.30%
Minimum Required for Capital Adequacy Purposes, Ratio	4.50%
Leverage Ratio:
Actual, Capital Amount	$ 750,023	$ 633,779	$ 696,963
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 357,549	$ 273,226	$ 251,133
Actual, Ratio	8.40%	9.30%	11.10%
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	$ 711,375	$ 654,031	$ 613,673
Minimum Required for Capital Adequacy Purposes, Capital Amount	483,284	455,633	403,840
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 604,105	$ 569,541	$ 504,799
Actual, Ratio	11.80%	11.50%	12.20%
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	$ 635,810	$ 582,783	$ 550,401
Minimum Required for Capital Adequacy Purposes, Capital Amount	362,463	227,816	201,920
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 483,284	$ 341,725	$ 302,880
Actual, Ratio	10.50%	10.20%	10.90%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	4.00%	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	8.00%	6.00%	6.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 635,810
Minimum Required for Capital Adequacy Purposes, Capital Amount	271,847
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 392,668
Actual, Ratio	10.50%
Minimum Required for Capital Adequacy Purposes, Ratio	4.50%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 635,810	$ 582,783	$ 550,401
Minimum Required for Capital Adequacy Purposes, Capital Amount	309,871	273,048	250,986
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 387,339	$ 341,310	$ 313,732
Actual, Ratio	8.20%	8.50%	8.80%
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%
The Bank of Holland [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 80,315
Minimum Required for Capital Adequacy Purposes, Capital Amount	60,686
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 75,857
Actual, Ratio	10.60%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	10.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 79,354
Minimum Required for Capital Adequacy Purposes, Capital Amount	45,514
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 60,686
Actual, Ratio	10.50%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	8.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 79,354
Minimum Required for Capital Adequacy Purposes, Capital Amount	34,136
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 49,307
Actual, Ratio	10.50%
Minimum Required for Capital Adequacy Purposes, Ratio	4.50%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 79,354
Minimum Required for Capital Adequacy Purposes, Capital Amount	32,387
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 40,484
Actual, Ratio	9.80%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	5.00%
The Bank of Northern Michigan [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 34,924
Minimum Required for Capital Adequacy Purposes, Capital Amount	25,673
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 32,091
Actual, Ratio	10.90%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	10.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 34,748
Minimum Required for Capital Adequacy Purposes, Capital Amount	19,255
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 25,673
Actual, Ratio	10.80%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	8.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 34,748
Minimum Required for Capital Adequacy Purposes, Capital Amount	14,441
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 20,859
Actual, Ratio	10.80%
Minimum Required for Capital Adequacy Purposes, Ratio	4.50%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 34,748
Minimum Required for Capital Adequacy Purposes, Capital Amount	15,408
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 19,260
Actual, Ratio	9.00%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	5.00%