Parent Company Only Financial Statements (Statements of Income) (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
Condensed Financial Statements, Captions [Line Items]
Other income									$ 11,988	$ 1,907	$ 697
Interest expense	$ 11,969	$ 6,753	$ 5,442	$ 5,134	$ 5,153	$ 5,234	$ 3,944	$ 3,450	29,298	17,781	14,710
Operating expenses	114,302	106,144	59,085	58,887	57,824	58,265	56,785	51,020	338,418	223,894	179,925
Income tax benefit	(18,969)	(2,848)	(10,532)	(9,757)	(10,200)	(9,600)	(9,100)	(8,100)	(42,106)	(37,000)	(27,500)
Net income	$ 47,168	$ 11,484	$ 25,775	$ 23,605	$ 25,504	$ 24,467	$ 19,024	$ 17,835	108,032	86,830	62,121
Chemical Financial Corporation
Condensed Financial Statements, Captions [Line Items]
Cash dividends from subsidiaries									110,450	56,860	64,468
Other income									151	144	95
Total income									110,601	57,004	64,563
Interest expense									1,816	761	42
Operating expenses									30,589	7,794	7,200
Total expenses									32,405	8,555	7,242
Income before income taxes and equity in undistributed net income of subsidiaries									78,196	48,449	57,321
Income tax benefit									11,378	2,582	2,302
Equity in undistributed net income of subsidiaries									18,458	35,799	2,498
Net income									$ 108,032	$ 86,830	$ 62,121