Earnings Per Common Share - Calculation of EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Basic Earnings Per Common Share:
Net income attributable to TCF Financial Corporation	$ 123,336	$ 51,899
Preferred stock dividends	2,493	2,493
Net income available to common stockholders	120,843	49,406
Less: Earnings allocated to participating securities	0	0
Earnings allocated to common stock	$ 120,843	$ 49,406
Weighted-average common shares outstanding used in basic earnings per common share calculation (in shares)	152,159,117	151,902,357
Basic earnings per common share (in usd per share)	$ 0.79	$ 0.33
Diluted Earnings Per Common Share:
Earnings allocated to common stock	$ 120,843	$ 49,406
Weighted-average common shares outstanding used in basic earnings per common share calculation (in shares)	152,159,117	151,902,357
Net dilutive effect of:
Non-participating restricted stock (in shares)	279,308	83,580
Stock options (in shares)	102,262	128,080
Weighted-average common shares outstanding used in diluted earnings per common share calculation (in shares)	152,540,687	152,114,017
Diluted earnings per common share (in usd per share)	$ 0.79	$ 0.32
Non-participating restricted stock
Anti-dilutive shares outstanding not included in the computation of diluted earnings per share:
Non-participating restricted stock (in shares)	324,514	1,173,331
Stock options
Anti-dilutive shares outstanding not included in the computation of diluted earnings per share:
Non-participating restricted stock (in shares)	74,376	90,144