Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income attributable to TCF Financial Corporation	$ 222,759	$ 295,468	$ 304,358
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on available-for-sale investment securities and interest-only strips	126,390	84,120	(11,669)
Net unrealized gains (losses) on net investment hedges	(4,195)	(5,186)	10,450
Foreign currency translation adjustment	5,894	8,514	(13,368)
Recognized postretirement prior service cost	307	(33)	(34)
Total other comprehensive income (loss), net of tax	128,396	87,415	(14,621)
Comprehensive income	$ 351,155	$ 382,883	$ 289,737