Parent Company Only Financial Statements Statements of Cash Flows (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Condensed Financial Statements, Captions [Line Items]
Net Income	$ 56,808	$ 51,008	$ 43,050
Net Cash Provided by (Used in) Operating Activities [Abstract]
Share-based compensation expense	2,854	1,865	1,517
Depreciation of premises and equipment	8,713	8,142	7,950
Net Cash Provided by Operating Activities	89,679	95,166	102,476
Net Cash Provided by (Used in) Investing Activities [Abstract]
Cash assumed in business combination	0	339,372	0
Purchase of investment securities available-for-sale	(304,264)	(191,689)	(419,714)
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	154,959	268,848	327,013
Purchases of premises and equipment, net	(8,664)	(10,303)	(8,602)
Net Cash Provided by (Used in) Investing Activities	(648,475)	53,127	(300,084)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Payments of Ordinary Dividends, Common Stock	(24,521)	(22,566)	(21,964)
Proceeds from Issuance of Common Stock	53,925	0	0
Proceeds from directors' stock purchase plan and exercise of stock options	806	260	245
Restricted Stock, Value, Shares Issued Net of Tax Withholdings	(379)	(248)	0
Net Cash Provided by Financing Activities	213,449	125,902	43,383
Net Increase (Decrease) in Cash and Cash Equivalents	(345,347)	274,195	(154,225)
Cash and Cash Equivalents at Beginning of Year	656,135	381,940	536,165
Cash and Cash Equivalents at End of Year	310,788	656,135	381,940
Chemical Financial Corporation [Member]
Condensed Financial Statements, Captions [Line Items]
Net Income	56,808	51,008	43,050
Net Cash Provided by (Used in) Operating Activities [Abstract]
Share-based compensation expense	2,854	1,865	1,517
Gain on sale of available-for-sale investment securities	(245)	0	0
Depreciation of premises and equipment	416	463	456
Equity in undistributed net income of subsidiary bank	(35,109)	(25,828)	(23,229)
Net increase in other assets	(711)	1,033	(975)
Net increase (decrease) in other liabilities	563	394	256
Net Cash Provided by Operating Activities	24,576	28,935	21,075
Net Cash Provided by (Used in) Investing Activities [Abstract]
Purchase of investment securities available-for-sale	0	(4,755)	0
Proceeds from Maturities, Prepayments and Calls of Available-for-sale Securities	5,000	0	0
Purchases of premises and equipment, net	(9)	(147)	(365)
Net Cash Provided by (Used in) Investing Activities	4,991	(4,902)	(365)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Payments of Ordinary Dividends, Common Stock	(24,521)	(22,566)	(21,964)
Proceeds from Issuance of Common Stock	53,925	0	0
Proceeds from directors' stock purchase plan and exercise of stock options	806	260	245
Restricted Stock, Value, Shares Issued Net of Tax Withholdings	(379)	(248)	0
Net Cash Provided by Financing Activities	29,831	(22,554)	(21,719)
Net Increase (Decrease) in Cash and Cash Equivalents	59,398	1,479	(1,009)
Cash and Cash Equivalents at Beginning of Year	5,960	4,481	5,490
Cash and Cash Equivalents at End of Year	$ 65,358	$ 5,960	$ 4,481