Earnings Per Common Share - Calculation of EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Basic Earnings Per Common Share:
Net income attributable to TCF Financial Corporation	$ 23,764	$ 90,427	$ 75,663	$ 160,921
Preferred stock dividends	2,494	2,494	4,987	4,987
Net income available to common stockholders	21,270	87,933	70,676	155,934
Less: Earnings allocated to participating securities	0	17	0	30
Earnings allocated to common stock	$ 21,270	$ 87,916	$ 70,676	$ 155,904
Weighted-average common shares outstanding used in basic earnings per common share calculation (in shares)	151,613,126	82,298,920	151,757,742	82,272,396
Basic earnings per common share (in usd per share)	$ 0.14	$ 1.07	$ 0.47	$ 1.89
Diluted Earnings Per Common Share:
Earnings allocated to common stock	$ 21,270	$ 87,916	$ 70,676	$ 155,904
Weighted-average common shares outstanding used in basic earnings per common share calculation (in shares)	151,613,126	82,298,920	151,757,742	82,272,396
Net dilutive effect of:
Non-participating restricted stock (in shares)	10,374	0	6,924	0
Stock options (in shares)	36,639	0	72,560	0
Weighted-average common shares outstanding used in diluted earnings per common share calculation (in shares)	151,660,139	82,298,920	151,837,226	82,272,396
Diluted earnings per common share (in usd per share)	$ 0.14	$ 1.07	$ 0.47	$ 1.89
Non-participating restricted stock
Anti-dilutive shares outstanding not included in the computation of diluted earnings per share:
Non-participating restricted stock (in shares)	2,702,972	914,459	2,962,872	914,459
Stock options
Anti-dilutive shares outstanding not included in the computation of diluted earnings per share:
Non-participating restricted stock (in shares)	358,522	0	259,900	0