Consolidated Statements of Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Interest income
Interest and fees on loans and leases	$ 1,430,628	$ 1,082,135	$ 966,928
Interest on investment securities:
Taxable	106,027	41,406	22,818
Tax-exempt	11,651	17,138	14,896
Interest on loans held-for-sale	18,599	6,686	16,612
Interest on other earning assets	20,356	11,964	10,491
Total interest income	1,587,261	1,159,329	1,031,745
Interest expense
Interest on deposits	226,157	107,690	66,464
Interest on borrowings	72,072	43,144	27,807
Total interest expense	298,229	150,834	94,271
Net interest income	1,289,032	1,008,495	937,474
Provision for credit losses	65,282	46,768	68,443
Net interest income after provision for credit losses	1,223,750	961,727	869,031
Noninterest income
Leasing revenue	163,718	172,603	134,460
Noninterest income	465,532	454,397	436,063
Net gains on sales of loans and leases	26,308	33,695	45,318
Net gains on investment securities	7,425	348	237
Other	21,811	28,769	23,969
Total noninterest income	465,532	454,397	436,063
Noninterest expense
Compensation and employee benefits	576,922	502,196	503,618
Occupancy and equipment	189,560	165,839	156,913
Lease financing equipment depreciation	76,426	73,829	55,901
Net foreclosed real estate and repossessed assets	13,523	17,050	17,756
Merger-related expenses	171,968	0	0
Other	303,716	255,486	325,746
Total noninterest expense	1,332,115	1,014,400	1,059,934
Income before income tax expense	357,167	401,724	245,160
Income tax expense (benefit)	50,241	86,096	(33,624)
Income after income tax expense (benefit)	306,926	315,628	278,784
Income attributable to non-controlling interest	11,458	11,270	10,147
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
Earnings per common share
Basic (in usd per share)	$ 2.56	$ 3.44	$ 2.83
Diluted (in usd per share)	$ 2.55	$ 3.43	$ 2.83
Weighted-average common shares outstanding
Basic (in shares)	111,604,094	84,133,983	85,706,054
Diluted (in shares)	111,818,365	84,324,686	85,734,575
Fees and service charges on deposit accounts
Noninterest income
Noninterest income	$ 127,860	$ 113,242	$ 115,567
Card and ATM revenue
Noninterest income
Noninterest income	87,221	78,406	75,165
Servicing fee revenue
Noninterest income
Noninterest income	20,776	27,334	41,347
Wealth management revenue
Noninterest income
Noninterest income	$ 10,413	$ 0	$ 0