Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Interest income
Interest and fees on loans and leases	$ 360,584	$ 443,096
Interest on investment securities:
Taxable	38,716	40,920
Tax-exempt	3,700	4,349
Interest on loans held-for-sale	975	1,561
Interest on other earning assets	1,657	5,466
Total interest income	405,632	495,392
Interest expense
Interest on deposits	13,786	67,419
Interest on borrowings	10,019	26,492
Total interest expense	23,805	93,911
Net interest income	381,827	401,481
Provision for credit losses	20,556	96,943
Net interest income after provision for credit losses	361,271	304,538
Noninterest income
Net gains on sales of loans and leases	6,058	7,573
Net gains on investment securities	8	0
Other	11,055	27,727
Total noninterest income	132,060	136,963
Noninterest expense
Compensation and employee benefits	173,602	171,528
Occupancy and equipment	52,166	57,288
Lease financing equipment depreciation	20,426	18,450
Net foreclosed real estate and repossessed assets	1,029	1,859
Merger-related expenses	16,216	36,728
Other	85,243	88,746
Total noninterest expense	348,682	374,599
Income before income tax expense	144,649	66,902
Income tax expense	19,540	13,086
Income after income tax expense	125,109	53,816
Income attributable to non-controlling interest	1,773	1,917
Net income attributable to TCF Financial Corporation	123,336	51,899
Preferred stock dividends	2,493	2,493
Net income available to common shareholders	$ 120,843	$ 49,406
Earnings per common share:
Basic earnings per common share (in usd per share)	$ 0.79	$ 0.33
Diluted earnings per common share (in usd per share)	$ 0.79	$ 0.32
Weighted-average common shares outstanding
Basic (in shares)	152,159,117	151,902,357
Diluted (in shares)	152,540,687	152,114,017
Leasing revenue
Interest expense
Revenue From Contract with Customer And Revenue Not From Contract With Customer, Excluding Interest Income	$ 36,453	$ 33,565
Noninterest income
Noninterest income	36,453	33,565
Fees and service charges on deposit accounts
Interest expense
Revenue From Contract with Customer And Revenue Not From Contract With Customer, Excluding Interest Income	25,895	34,597
Noninterest income
Noninterest income	25,895	34,597
Total noninterest income	25,895	34,597
Card and ATM revenue
Interest expense
Revenue From Contract with Customer And Revenue Not From Contract With Customer, Excluding Interest Income	24,661	21,685
Noninterest income
Noninterest income	24,661	21,685
Total noninterest income	24,661	21,685
Mortgage banking income
Interest expense
Revenue From Contract with Customer And Revenue Not From Contract With Customer, Excluding Interest Income	20,986	5,665
Noninterest income
Noninterest income	20,986	5,665
Wealth management revenue
Interest expense
Revenue From Contract with Customer And Revenue Not From Contract With Customer, Excluding Interest Income	6,944	6,151
Noninterest income
Noninterest income	6,944	6,151
Total noninterest income	$ 6,944	$ 6,151