Equity - Preferred Stock (Details) - USD ($) $ / shares in Units, $ in Thousands			12 Months Ended
	Aug. 01, 2019	Mar. 01, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Preferred Stock Information
Preferred stock, par value (in dollars per share)			$ 0.01	$ 0.01
Preferred stock, shares outstanding (in shares)			7,000	7,000
Series C non-cumulative perpetual preferred stock
Preferred Stock Information
Preferred stock, value outstanding			$ 169,302	$ 169,302
Dividend rate on preferred stock	5.70%		5.70%	5.70%	5.70%
Preferred stock, liquidation preference per share	$ 25,000			$ 25,000
Preferred stock, par value (in dollars per share)	0.01			0.01
Preferred stock, liquidation preference per depositary share	$ 25			$ 25
Preferred stock, depositary shares outstanding	7,000,000			7,000,000
Series B non-cumulative perpetual preferred stock
Preferred Stock Information
Dividend rate on preferred stock		6.45%		6.45%	6.45%
Preferred stock, par value (in dollars per share)		$ 0.01
Redemption of Preferred Stock (in shares)		4,000,000
Deferred stock issuance costs of preferred stock		$ 3,500
Redemption of Preferred Stock		$ 100,000		$ 100,000
Chemical Financial Corporation | Preferred Stock
Preferred Stock Information
Dividend rate on preferred stock	5.70%
Preferred stock, liquidation preference per share	$ 25,000
Share conversion ratio (in shares)	1
Preferred stock, shares outstanding (in shares)	7,000