Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income attributable to TCF Financial Corporation	$ 55,738	$ 22,148	$ 131,401	$ 183,069
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on available-for-sale investment securities and interest-only strips	(7,694)	19,230	138,550	87,223
Net unrealized gains (losses) on net investment hedges	(2,655)	1,641	3,269	(2,846)
Foreign currency translation adjustment	3,721	(1,968)	(4,298)	5,014
Recognized postretirement prior service cost	(9)	(9)	(27)	(25)
Total other comprehensive income (loss), net of tax	(6,637)	18,894	137,494	89,366
Comprehensive income	$ 49,101	$ 41,042	$ 268,895	$ 272,435