Regulatory Capital (Details) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk weighted assets	$ 6,990,000	$ 5,700,000	$ 4,900,000
Chemical Financial Corporation [Member]
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount	816,595	705,130	748,332
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 559,273	$ 456,302	$ 391,911
Actual, Ratio	11.70%	12.40%	15.30%
Minimum Required for Capital Adequacy Purposes, Ratio	8.00%	8.00%	8.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount	$ 741,654	$ 633,779	$ 686,892
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 419,455	$ 228,151	$ 195,955
Actual, Ratio	10.60%	11.10%	14.00%
Minimum Required for Capital Adequacy Purposes, Ratio	6.00%	4.00%	4.00%
Common Equity Tier One Risk Based Capital	$ 723,654
Common Equity Tier One Risk Based Capital to Risk Weighted Assets	10.40%
Common Equity Tier One Risk Based Capital for Capital Adequacy	$ 314,591
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Leverage Ratio:
Actual, Capital Amount	$ 741,654	$ 633,779	$ 686,892
Minimum Required for Capital Adequacy Purposes, Capital Amount	$ 314,344	$ 273,226	$ 244,757
Actual, Ratio	9.40%	9.30%	11.20%
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	$ 713,999	$ 654,031	$ 601,561
Minimum Required for Capital Adequacy Purposes, Capital Amount	471,422	455,633	391,305
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 589,277	$ 569,541	$ 489,131
Actual, Ratio	12.10%	11.50%	12.30%
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	$ 640,324	$ 582,783	$ 540,214
Minimum Required for Capital Adequacy Purposes, Capital Amount	353,566	227,816	195,653
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 471,422	$ 341,725	$ 293,479
Actual, Ratio	10.90%	10.20%	11.00%
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 One Risk Based Capital	$ 640,324
Common Equity Tier One Risk Based Capital to Risk Weighted Assets	10.90%
Common Equity Tier One Risk Based Capital for Capital Adequacy	$ 265,175
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Common Equity Tier One Risk Based Capital to be Well Capitalized	$ 383,030
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized to Risk Weighted Assets	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 640,324	$ 582,783	$ 540,214
Minimum Required for Capital Adequacy Purposes, Capital Amount	300,703	273,048	244,604
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 375,878	$ 341,310	$ 305,755
Actual, Ratio	8.50%	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	$ 72,506
Minimum Required for Capital Adequacy Purposes, Capital Amount	61,028
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 76,285
Actual, Ratio	9.50%
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	$ 72,506
Minimum Required for Capital Adequacy Purposes, Capital Amount	45,771
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 61,028
Actual, Ratio	9.50%
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 One Risk Based Capital	$ 72,506
Common Equity Tier One Risk Based Capital to Risk Weighted Assets	9.50%
Common Equity Tier One Risk Based Capital for Capital Adequacy	$ 34,328
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Common Equity Tier One Risk Based Capital to be Well Capitalized	$ 49,585
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized to Risk Weighted Assets	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 72,506
Minimum Required for Capital Adequacy Purposes, Capital Amount	30,710
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 38,388
Actual, Ratio	9.40%
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	$ 32,779
Minimum Required for Capital Adequacy Purposes, Capital Amount	25,878
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 32,347
Actual, Ratio	10.10%
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	$ 32,779
Minimum Required for Capital Adequacy Purposes, Capital Amount	19,408
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 25,878
Actual, Ratio	10.10%
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 One Risk Based Capital	$ 32,779
Common Equity Tier One Risk Based Capital to Risk Weighted Assets	10.10%
Common Equity Tier One Risk Based Capital for Capital Adequacy	$ 14,556
Common Equity Tier One Risk Based Capital Required for Capital Adequacy to Risk Weighted Assets	4.50%
Common Equity Tier One Risk Based Capital to be Well Capitalized	$ 21,025
Common Equity Tier One Risk Based Capital Required to Be Well Capitalized to Risk Weighted Assets	6.50%
Leverage Ratio:
Actual, Capital Amount	$ 32,779
Minimum Required for Capital Adequacy Purposes, Capital Amount	14,421
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount	$ 18,026
Actual, Ratio	9.10%
Minimum Required for Capital Adequacy Purposes, Ratio	4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio	5.00%