Earnings Per Common Share - Calculation of EPS (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Basic Earnings Per Common Share:
Net income attributable to TCF Financial Corporation	$ 22,148	$ 86,196	$ 183,069	$ 218,706
Preferred stock dividends	2,494	2,494	7,481	9,094
Impact of preferred stock redemption	0	0	0	3,481
Net income available to common stockholders	19,654	83,702	175,588	206,131
Less: Earnings allocated to participating securities	0	13	19	30
Earnings allocated to common stock	$ 19,654	$ 83,689	$ 175,569	$ 206,101
Weighted-average common shares outstanding used in basic earnings per common share calculation (in shares)	128,575,171	83,762,625	97,876,262	84,522,519
Basic earnings per common share (in usd per share)	$ 0.15	$ 1.00	$ 1.79	$ 2.44
Diluted Earnings Per Common Share:
Earnings allocated to common stock	$ 19,654	$ 83,689	$ 175,569	$ 206,101
Weighted-average common shares outstanding used in basic earnings per common share calculation (in shares)	128,575,171	83,762,625	97,876,262	84,522,519
Net dilutive effect of:
Non-participating restricted stock (in shares)	73,698	0	139,795	0
Stock options (in shares)	105,719	0	39,222	1,670
Warrants (in shares)	0	45,438	0	266,935
Weighted-average common shares outstanding used in diluted earnings per common share calculation (in shares)	128,754,588	83,808,063	98,055,279	84,791,124
Diluted earnings per common share (in usd per share)	$ 0.15	$ 1.00	$ 1.79	$ 2.43
Anti-dilutive shares outstanding not included in the computation of diluted earnings per share:
Non-participating restricted stock (in shares)	1,369,025	1,058,202	1,369,025	1,058,202