Earnings Per Common Share - Computations of basic and diluted earnings per common share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Basic Earnings Per Common Share:
Net income attributable to TCF Financial Corporation	$ 112,399	$ 22,148	$ 90,427	$ 70,494	$ 85,652	$ 86,196	$ 58,749	$ 73,761	$ 295,468	$ 304,358	$ 268,637
Preferred stock dividends	2,494	2,494	2,494	2,493	2,494	2,494	2,494	4,106	9,975	11,588	19,904
Impact of preferred stock redemption	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 0	$ 3,481	0	3,481	5,779
Net income available to common shareholders									285,493	289,289	242,954
Less: Earnings allocated to participating securities									20	42	42
Earnings allocated to common stock									$ 285,473	$ 289,247	$ 242,912
Weighted-average common shares outstanding used in basic earnings per common share calculation (in shares)									111,604,094	84,133,983	85,706,054
Basic earnings per common share (in dollars per share)	$ 0.72	$ 0.15	$ 1.07	$ 0.83	$ 1.00	$ 1.00	$ 0.67	$ 0.77	$ 2.56	$ 3.44	$ 2.83
Diluted Earnings Per Common Share:
Earnings allocated to common stock									$ 285,473	$ 289,247	$ 242,912
Weighted-average common shares outstanding used in basic earnings per common share calculation (in shares)									111,604,094	84,133,983	85,706,054
Net dilutive effect of:
Non-participating restricted stock (in shares)									140,832	0	0
Stock options (in shares)									73,439	1,184	14,544
Warrants (in shares)									0	189,519	13,977
Weighted-average common shares outstanding used in diluted earnings per common share calculation (in shares)									111,818,365	84,324,686	85,734,575
Diluted earnings per common share (in dollars per share)	$ 0.72	$ 0.15	$ 1.07	$ 0.83	$ 1.00	$ 1.00	$ 0.67	$ 0.77	$ 2.55	$ 3.43	$ 2.83
Non-participating restricted stock
Net dilutive effect of:
Anti-dilutive shares outstanding not included in the computation of diluted earnings per common share (in shares)									1,288,539	1,028,942	1,163,382
Stock options
Net dilutive effect of:
Anti-dilutive shares outstanding not included in the computation of diluted earnings per common share (in shares)									97,980	0	0