Parent Company Financial Information - Condensed Statements of Income (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income:
Interest income									$ 1,587,261	$ 1,159,329	$ 1,031,745
Interest expense									298,229	150,834	94,271
Net interest income	$ 408,753	$ 371,793	$ 254,057	$ 254,429	$ 253,153	$ 253,502	$ 254,751	$ 247,089	1,289,032	1,008,495	937,474
Non-interest income:
Total noninterest income	158,052	94,258	109,718	103,504	123,868	112,064	110,151	108,314	465,532	454,397	436,063
Non-interest expense:
Compensation and employee benefits									576,922	502,196	503,618
Occupancy and equipment									189,560	165,839	156,913
Merger-related expenses									171,968	0	0
Other									303,716	255,486	325,746
Total noninterest expense	416,571	425,620	236,849	253,075	249,958	246,423	272,039	245,980	1,332,115	1,014,400	1,059,934
Income before income tax expense	135,831	13,243	113,357	94,736	108,169	116,873	78,627	98,055	357,167	401,724	245,160
Income tax benefit	(21,375)	11,735	(19,314)	(21,287)	(20,013)	(28,034)	(16,418)	(21,631)	(50,241)	(86,096)	33,624
Net income attributable to TCF Financial Corporation	112,399	22,148	90,427	70,494	85,652	86,196	58,749	73,761	295,468	304,358	268,637
Preferred stock dividends	2,494	2,494	2,494	2,493	2,494	2,494	2,494	4,106	9,975	11,588	19,904
Impact of preferred stock redemption	0	0	0	0	0	0	0	3,481	0	3,481	5,779
Net income available to common shareholders	$ 109,905	$ 19,654	$ 87,933	$ 68,001	$ 83,158	83,702	$ 56,255	$ 66,174	285,493	289,289	242,954
TCF Financial Corporation
Interest income:
Interest income									262	200	183
Interest expense						$ 0			484		0
Net interest income									(222)	200	183
Non-interest income:
Dividends from TCF Bank									225,000	431,000	65,000
Management fees									14,001	20,532	15,660
Other									581	426	13
Total noninterest income									239,582	451,958	80,673
Non-interest expense:
Compensation and employee benefits									18,677	20,282	16,233
Occupancy and equipment									470	301	275
Merger-related expenses									69,944	0	0
Other									5,040	5,682	3,353
Total noninterest expense									94,131	26,265	19,861
Income before income tax expense									145,229	425,893	60,995
Income tax benefit									15,513	952	1,575
Income before equity in undistributed earnings (loss) of TCF Bank									160,742	426,845	62,570
Equity in undistributed earnings (loss) of TCF Bank									134,726	(122,487)	206,067
Net income attributable to TCF Financial Corporation									295,468	304,358	268,637
Preferred stock dividends									9,975	11,588	19,904
Impact of preferred stock redemption									0	3,481	5,779
Net income available to common shareholders									$ 285,493	$ 289,289	$ 242,954