Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
Net income attributable to TCF Financial Corporation	$ 123,336	$ 51,899
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on available-for-sale investment securities and interest-only strips	(180,612)	115,847
Net unrealized gains (losses) on net investment hedges	(1,559)	10,481
Foreign currency translation adjustment	2,170	(14,426)
Recognized postretirement prior service cost	(18)	(9)
Total other comprehensive income (loss), net of tax	(180,019)	111,893
Comprehensive (loss) income	$ (56,683)	$ 163,792