Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income attributable to TCF Financial Corporation	$ 23,764	$ 90,427	$ 75,663	$ 160,921
Other comprehensive income (loss), net of tax:
Net unrealized gains (losses) on available-for-sale investment securities and interest-only strips	30,397	30,625	146,244	67,993
Net unrealized gains (losses) on net investment hedges	(4,557)	(2,179)	5,924	(4,487)
Foreign currency translation adjustment	6,407	3,415	(8,019)	6,982
Recognized postretirement prior service cost	(9)	(8)	(18)	(16)
Total other comprehensive income (loss), net of tax	32,238	31,853	144,131	70,472
Comprehensive income	$ 56,002	$ 122,280	$ 219,794	$ 231,393