Parent Company Only Financial Statements (Financial Position) (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	May 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Assets
Premises and equipment	$ 145,012	$ 106,317
Goodwill	1,133,534	287,393
Other assets	650,973	246,346
Total assets	17,355,179	9,188,797
Liabilities and Equity [Abstract]
Other liabilities	134,637	76,466
Subordinated debentures			$ 18,600
Total liabilities	14,773,653	8,172,823
Shareholders' equity	2,581,526	1,015,974		$ 797,133	$ 696,500
Total liabilities and shareholders' equity	17,355,179	9,188,797
Chemical Financial Corporation
Assets
Cash at subsidiary bank	16,851	28,884
Investment in subsidiaries	2,654,458	1,023,285
Premises and equipment	4,051	3,632
Goodwill	1,092	1,092
Other assets	63,584	13,051
Total assets	2,740,036	1,069,944
Liabilities and Equity [Abstract]
Other liabilities	18,345	10,426
Non-revolving line-of-credit	124,625	25,000
Subordinated debentures	15,540	18,544
Total liabilities	158,510	53,970
Shareholders' equity	2,581,526	1,015,974
Total liabilities and shareholders' equity	$ 2,740,036	$ 1,069,944