Parent Company Only Financial Statements (Statements of Cash Flows) (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	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
Cash Flows From Operating Activities
Net Income	$ 47,168	$ 11,484	$ 25,775	$ 23,605	$ 25,504	$ 24,467	$ 19,024	$ 17,835	$ 108,032	$ 86,830	$ 62,121
Share-based compensation expense									13,452	3,478	2,931
Depreciation									13,270	11,028	8,980
Net cash from operating activities									280,578	103,049	90,225
Cash Flows From Investing Activities
Net cash acquired (paid) in business combinations									325,714	16,551	(14,260)
Purchases of premises and equipment, net									(18,098)	(8,527)	(13,411)
Net cash used in investing activities									(542,946)	(408,784)	(479,049)
Cash Flows From Financing Activities
Cash dividends paid									(49,389)	(36,918)	(29,528)
Proceeds from issuance of common stock, net of issuance costs									0	0	76,175
Repayments of other borrowings									(351,018)	(6,000)	(10,310)
Proceeds from issuance of other borrowings									375,000	125,000	0
Proceeds from directors' stock purchase plan and exercise of stock options									1,572	2,473	1,242
Cash paid for payroll taxes upon conversion of restricted stock units									(1,065)	(571)	(701)
Net cash from financing activities									497,981	361,504	261,056
Net increase (decrease) in cash and cash equivalents									235,613	55,769	(127,768)
Cash and cash equivalents at beginning of year				238,789				183,020	238,789	183,020	310,788
Cash and cash equivalents at end of year	474,402				238,789				474,402	238,789	183,020
Business combinations:
Fair value of tangible assets acquired (noncash)									6,371,781	1,282,420	747,181
Liabilities assumed									6,100,901	1,258,051	815,011
Common stock and stock options issued									1,504,811	159,904	0
Chemical Financial Corporation
Cash Flows From Operating Activities
Net Income									108,032	86,830	62,121
Share-based compensation expense									13,452	3,478	2,931
Depreciation									355	318	327
Equity in undistributed net income of subsidiaries									(18,458)	(35,799)	(2,498)
Net decrease in other assets									9,752	2,873	1,101
Net decrease in other liabilities									(11,830)	(19,033)	(2,519)
Net cash from operating activities									101,303	38,667	61,463
Cash Flows From Investing Activities
Net cash acquired (paid) in business combinations									(107,622)	(45,267)	(117,853)
Purchases of premises and equipment, net									(774)	(320)	(26)
Net cash used in investing activities									(108,396)	(45,587)	(117,879)
Cash Flows From Financing Activities
Cash dividends paid									(49,389)	(36,918)	(29,528)
Proceeds from issuance of common stock, net of issuance costs									0	0	76,175
Repayment of subordinated debt obligations									(18,558)	0	(10,310)
Repayments of other borrowings									(62,500)	0	0
Proceeds from issuance of other borrowings									125,000	25,000	0
Proceeds from directors' stock purchase plan and exercise of stock options									1,572	2,473	1,242
Cash paid for payroll taxes upon conversion of restricted stock units									(1,065)	(571)	(701)
Net cash from financing activities									(4,940)	(10,016)	36,878
Net increase (decrease) in cash and cash equivalents									(12,033)	(16,936)	(19,538)
Cash and cash equivalents at beginning of year				$ 28,884				$ 45,820	28,884	45,820	65,358
Cash and cash equivalents at end of year	$ 16,851				$ 28,884				16,851	28,884	45,820
Business combinations:
Fair value of tangible assets acquired (noncash)									46,898	10,304	1,537
Liabilities assumed									58,309	42,019	13,010
Common stock and stock options issued									$ 1,504,811	$ 159,904	$ 0