Parent Company Only Financial Statements Statements of Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Condensed Financial Statements, Captions [Line Items]
Other income									$ 647	$ 861	$ 1,202
Operating expenses	52,616	42,702	42,425	42,182	42,405	39,545	41,041	41,957	179,925	164,948	151,921
Federal income tax benefit	(7,050)	(7,450)	(7,100)	(5,900)	(6,100)	(6,400)	(6,100)	(5,700)	(27,500)	(24,300)	(20,800)
Net Income	15,305	16,767	16,236	13,813	14,378	14,993	14,203	13,234	62,121	56,808	51,008
Chemical Financial Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Cash dividends from subsidiary bank									64,468	24,488	27,550
Other income									53	390	92
Total income									64,521	24,878	27,642
Operating expenses									7,200	4,735	3,773
Income (loss) before income taxes and equity in undistributed net income of subsidiary bank									57,321	20,143	23,869
Federal income tax benefit									2,302	1,556	1,311
Equity in undistributed net income of subsidiary bank									2,498	35,109	25,828
Net Income									$ 62,121	$ 56,808	$ 51,008