Regulatory Capital and Reserve Requirements (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
	Feb. 20, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Minimum average regulatory cash reserve balance		$ 52,300				$ 65,300				$ 52,300	$ 65,300
Leverage Ratio:
Cash dividends declared per share (in dollars per share)		$ 0.27	$ 0.27	$ 0.26	$ 0.26	$ 0.26	$ 0.26	$ 0.24	$ 0.24	$ 1.06	$ 1.00	$ 0.94
Subsequent Event
Leverage Ratio:
Cash dividends declared per share (in dollars per share)	$ 0.27
Chemical Financial Corporation
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk weighted assets		$ 13,420,000				$ 7,140,000				$ 13,420,000	$ 7,140,000
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount		$ 1,543,018				$ 841,257				$ 1,543,018	$ 841,257
Actual, Ratio		11.50%				11.80%				11.50%	11.80%
Minimum Required for Capital Adequacy Purposes, Capital Amount		$ 1,073,431				$ 571,509				$ 1,073,431	$ 571,509
Minimum Required for Capital Adequacy Purposes, Ratio		8.00%				8.00%				8.00%	8.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,157,293								$ 1,157,293
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		8.60%								8.60%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount		$ 1,441,209				$ 767,929				$ 1,441,209	$ 767,929
Actual, Ratio		10.70%				10.70%				10.70%	10.70%
Minimum Required for Capital Adequacy Purposes, Capital Amount		$ 805,073				$ 428,631				$ 805,073	$ 428,631
Minimum Required for Capital Adequacy Purposes, Ratio		6.00%				6.00%				6.00%	6.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 888,935								$ 888,935
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		6.60%								6.60%
Common Equity Tier 1 Capital to Risk-Weighted Assets
Actual, Capital Amount		$ 1,441,209				$ 753,815				$ 1,441,209	$ 753,815
Minimum Required for Capital Adequacy Purposes, Capital Amount		10.70%				10.60%				10.70%	10.60%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount		$ 603,805				$ 321,474				$ 603,805	$ 321,474
Actual, Ratio		4.50%				4.50%				4.50%	4.50%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 687,667								$ 687,667
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		5.10%								5.10%
Leverage Ratio:
Actual, Capital Amount		$ 1,441,209				$ 767,929				$ 1,441,209	$ 767,929
Actual, Ratio		9.00%				8.60%				9.00%	8.60%
Minimum Required for Capital Adequacy Purposes, Capital Amount		$ 643,603				$ 356,396				$ 643,603	$ 356,396
Minimum Required for Capital Adequacy Purposes, Ratio		4.00%				4.00%				4.00%	4.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 643,603								$ 643,603
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		4.00%								4.00%
Cash dividends from subsidiaries										$ 110,450	$ 56,860	$ 64,468
Chemical Bank
Compliance with Regulatory Capital Requirements under Banking Regulations [Line Items]
Risk weighted assets		$ 13,360,000				$ 7,130,000				13,360,000	7,130,000
Total Capital to Risk-Weighted Assets:
Actual, Capital Amount		$ 1,608,980				$ 830,294				$ 1,608,980	$ 830,294
Actual, Ratio		12.00%				11.70%				12.00%	11.70%
Minimum Required for Capital Adequacy Purposes, Capital Amount		$ 1,068,560				$ 570,073				$ 1,068,560	$ 570,073
Minimum Required for Capital Adequacy Purposes, Ratio		8.00%				8.00%				8.00%	8.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 1,152,041								$ 1,152,041
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		8.60%								8.60%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount		$ 1,335,700				$ 712,591				$ 1,335,700	$ 712,591
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio		10.00%				10.00%				10.00%	10.00%
Tier 1 Capital to Risk-Weighted Assets:
Actual, Capital Amount		$ 1,522,711				$ 756,966				$ 1,522,711	$ 756,966
Actual, Ratio		11.40%				10.60%				11.40%	10.60%
Minimum Required for Capital Adequacy Purposes, Capital Amount		$ 801,420				$ 427,555				$ 801,420	$ 427,555
Minimum Required for Capital Adequacy Purposes, Ratio		6.00%				6.00%				6.00%	6.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 884,901								$ 884,901
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		6.60%								6.60%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount		$ 1,068,560				$ 570,073				$ 1,068,560	$ 570,073
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio		8.00%				8.00%				8.00%	8.00%
Common Equity Tier 1 Capital to Risk-Weighted Assets
Actual, Capital Amount		$ 1,522,711				$ 756,966				$ 1,522,711	$ 756,966
Minimum Required for Capital Adequacy Purposes, Capital Amount		11.40%				10.60%				11.40%	10.60%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount		$ 601,065				$ 320,666				$ 601,065	$ 320,666
Actual, Ratio		4.50%				4.50%				4.50%	4.50%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 684,546								$ 684,546
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		5.10%								5.10%
Minimum Required for Capital Adequacy Purposes, Ratio		$ 868,205				$ 463,184				$ 868,205	$ 463,184
Required to be Well Capital Under Prompt Corrective Action Regulations, Ratio		6.50%				6.50%				6.50%	6.50%
Leverage Ratio:
Actual, Capital Amount		$ 1,522,711				$ 756,966				$ 1,522,711	$ 756,966
Actual, Ratio		9.50%				8.50%				9.50%	8.50%
Minimum Required for Capital Adequacy Purposes, Capital Amount		$ 641,457				$ 355,911				$ 641,457	$ 355,911
Minimum Required for Capital Adequacy Purposes, Ratio		4.00%				4.00%				4.00%	4.00%
For Capital Adequacy Purposes Plus Capital Conservation Buffer Amount		$ 641,457								$ 641,457
For Capital Adequacy Purposes Plus Capital Conservation Buffer Ratio		4.00%								4.00%
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Capital Amount		$ 801,822				$ 444,888				$ 801,822	$ 444,888
Required to be Well Capitalized Under Prompt Corrective Action Regulations, Ratio		5.00%				5.00%				5.00%	5.00%