Consolidated Statements of Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Interest income
Interest and fees on loans and leases	$ 373,112	$ 417,370	$ 1,209,034	$ 983,890
Interest on investment securities:
Taxable	35,648	31,038	109,073	69,745
Tax-exempt	3,892	3,385	12,396	7,277
Interest on loans held-for-sale	3,829	1,408	8,712	2,832
Interest on other earning assets	3,967	6,607	14,995	13,739
Total interest income	420,448	459,808	1,354,210	1,077,483
Interest expense
Interest on deposits	31,852	70,900	146,056	149,154
Interest on borrowings	11,429	17,115	51,147	48,050
Total interest expense	43,281	88,015	197,203	197,204
Net interest income	377,167	371,793	1,157,007	880,279
Provision for credit losses	69,664	27,188	245,333	50,879
Net interest income after provision for credit losses	307,503	344,605	911,674	829,400
Noninterest income
Noninterest income	118,810	94,258	388,827	307,480
Net gains (losses) on sales of loans and leases	23,490	(5,984)	73,114	13,374
Net gains on investment securities	2,324	5,900	2,332	7,417
Other	5,411	(12,309)	33,119	(312)
Total noninterest income	118,810	94,258	388,827	307,480
Noninterest expense
Compensation and employee benefits	168,323	155,745	511,650	395,953
Occupancy and equipment	48,233	49,229	159,628	132,789
Lease financing equipment depreciation	17,932	19,408	54,594	57,797
Net foreclosed real estate and repossessed assets	1,518	2,203	4,375	9,281
Merger-related expenses	54,011	111,259	172,358	124,943
Other	83,423	87,776	245,675	194,781
Total noninterest expense	373,440	425,620	1,148,280	915,544
Income before income tax (benefit) expense	52,873	13,243	152,221	221,336
Income tax (benefit) expense	(4,429)	(11,735)	14,870	28,866
Income after income tax (benefit) expense	57,302	24,978	137,351	192,470
Income attributable to non-controlling interest	1,564	2,830	5,950	9,401
Net income attributable to TCF Financial Corporation	55,738	22,148	131,401	183,069
Preferred stock dividends	2,494	2,494	7,481	7,481
Net income available to common shareholders	$ 53,244	$ 19,654	$ 123,920	$ 175,588
Earnings per common share:
Basic earnings per common share (in usd per share)	$ 0.35	$ 0.15	$ 0.82	$ 1.79
Diluted earnings per common share (in usd per share)	$ 0.35	$ 0.15	$ 0.82	$ 1.79
Weighted-average common shares outstanding
Basic (in shares)	151,768,337	128,575,171	151,761,299	97,876,262
Diluted (in shares)	151,821,592	128,754,588	151,826,928	98,055,279
Leasing revenue
Noninterest income
Noninterest income	$ 31,905	$ 39,590	$ 102,642	$ 117,032
Fees and service charges on deposit accounts
Noninterest income
Noninterest income	25,470	34,384	82,899	88,504
Card and ATM revenue
Noninterest income
Noninterest income	23,383	23,315	65,704	62,470
Wealth management revenue
Noninterest income
Noninterest income	6,506	4,241	18,863	4,241
Servicing fee revenue
Noninterest income
Noninterest income	$ 321	$ 5,121	$ 10,154	$ 14,754