Selected Quarterly Financial Data - Summary of Selected Quarterly Financial Data (Details) - USD ($) $ / shares in Units, $ 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
Quarterly Financial Information Disclosure [Abstract]
Net interest income	$ 381,394	$ 377,167	$ 378,359	$ 401,481	$ 408,753	$ 371,793	$ 254,057	$ 254,429	$ 1,538,401	$ 1,289,032	$ 1,008,495
Provision for credit losses	11,818	69,664	78,726	96,943	14,403	27,188	13,569	10,122	257,151	65,282	46,768
Net interest income after provision for credit losses	369,576	307,503	299,633	304,538	394,350	344,605	240,488	244,307	1,281,250	1,223,750	961,727
Noninterest income	127,236	118,810	133,054	136,963	158,052	94,258	109,718	103,504	516,063	465,532	454,397
Noninterest expense	379,091	373,440	400,241	374,599	416,571	425,620	236,849	253,075	1,527,371	1,332,115	1,014,400
Income before income tax expense	117,721	52,873	32,446	66,902	135,831	13,243	113,357	94,736	269,942	357,167	401,724
Income tax expense (benefit)	25,031	(4,429)	6,213	13,086	21,375	(11,735)	19,314	21,287	39,901	50,241	86,096
Income after income tax expense	92,690	57,302	26,233	53,816	114,456	24,978	94,043	73,449	230,041	306,926	315,628
Income attributable to non-controlling interest	1,332	1,564	2,469	1,917	2,057	2,830	3,616	2,955	7,282	11,458	11,270
Net income attributable to TCF Financial Corporation	91,358	55,738	23,764	51,899	112,399	22,148	90,427	70,494	222,759	295,468	304,358
Preferred stock dividends	2,494	2,494	2,494	2,493	2,494	2,494	2,494	2,493	9,975	9,975	11,588
Net income available to common shareholders	$ 88,864	$ 53,244	$ 21,270	$ 49,406	$ 109,905	$ 19,654	$ 87,933	$ 68,001	$ 212,784	$ 285,493	$ 289,289
Basic (in usd per share)	$ 0.58	$ 0.35	$ 0.14	$ 0.33	$ 0.72	$ 0.15	$ 1.07	$ 0.83	$ 1.40	$ 2.56	$ 3.44
Diluted (in usd per share)	$ 0.58	$ 0.35	$ 0.14	$ 0.32	$ 0.72	$ 0.15	$ 1.07	$ 0.83	$ 1.40	$ 2.55	$ 3.43