Parent Company Financial Information - Condensed Statements of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Condensed Statements of Cash Flows
Net income	$ 91,358	$ 55,738	$ 23,764	$ 51,899	$ 112,399	$ 22,148	$ 90,427	$ 70,494	$ 222,759	$ 295,468	$ 304,358
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Depreciation and amortization									437,585	308,638	204,778
Provision (benefit) for deferred income taxes									(74,841)	30,410	58,986
Net gains on sales of assets									(90,299)	(66,298)	(39,881)
Net change in other assets									(484,298)	(263,351)	(35,154)
Net change in other liabilities									(119,586)	162,533	39,898
Other, net									(78,131)	(65,921)	(41,949)
Net cash provided by (used in) operating activities									121,106	641,757	563,630
Cash flows from investing activities
Proceeds from sales of other assets									(188,378)	(154,540)	(155,664)
Net cash provided by (used in) investing activities									(1,237,929)	666,876	(902,294)
Cash flows from financing activities
Redemption of preferred stock									0	0	(100,000)
Repurchases of common stock									(33,098)	(86,309)	(212,929)
Common shares sold to TCF employee benefit plans									0	0	715
Dividends paid on preferred stock									(9,975)	(9,975)	(11,588)
Dividends paid on common stock									(214,687)	(156,060)	(99,490)
Payments related to tax-withholding upon conversion of share-based awards									(4,553)	(6,198)	(6,865)
Exercise of stock options									2,100
Net cash provided by (used in) financing activities									1,149,047	(667,319)	303,939
Net change in cash and due from banks									32,224	641,314	(34,725)
Cash and due from banks at beginning of period				491,787					491,787
Cash and due from banks at end of period	531,918				491,787				531,918	491,787
TCF Financial Corporation
Condensed Statements of Cash Flows
Net income									222,759	295,468	304,358
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Equity in undistributed (earnings) loss of TCF Bank									2,672	(134,726)	122,487
Compensation and employee benefits									35,439	28,351	17,824
Depreciation and amortization									(99)	(640)	4,986
Provision (benefit) for deferred income taxes									(352)	4,893	(583)
Net gains on sales of assets									0	6	(402)
Net change in other assets									(10,572)	(1,072)	753
Net change in other liabilities									30,900	(1,154)	(374)
Other, net									(1,332)	(21,719)	(7,958)
Net cash provided by (used in) operating activities									279,415	169,407	441,091
Cash flows from investing activities
Proceeds from sales of other assets									(23)	(95)	(3)
Proceeds from sales of premises and equipment									0	17	727
Net cash acquired in business combination									0	155,155	0
Net cash provided by (used in) investing activities									(23)	155,077	724
Cash flows from financing activities
Redemption of preferred stock									0	0	(100,000)
Repurchases of common stock									(33,098)	(86,309)	(212,929)
Common shares sold to TCF employee benefit plans									0	0	715
Dividends paid on preferred stock									(9,975)	(9,975)	(11,588)
Dividends paid on common stock									(214,687)	(156,060)	(99,490)
Payments related to tax-withholding upon conversion of share-based awards									(4,555)	(6,198)	(6,865)
Exercise of stock options									(23)	29	(997)
Net cash provided by (used in) financing activities									(262,338)	(258,513)	(431,154)
Net change in cash and due from banks									17,054	65,971	10,661
Cash and due from banks at beginning of period				$ 157,103				$ 91,132	157,103	91,132	80,471
Cash and due from banks at end of period	$ 174,157				$ 157,103				$ 174,157	$ 157,103	$ 91,132