Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cash flows from operating activities
Net income	$ 230,041	$ 306,926	$ 315,628
Adjustments to reconcile net income to net cash provided by (used in) operating activities:
Provision for credit losses	257,151	65,282	46,768
Share-based compensation expense	35,438	28,351	17,824
Depreciation and amortization	437,585	308,638	204,778
Provision (benefit) for deferred income taxes	(74,841)	30,410	58,986
Net gains on sales of assets	(90,299)	(66,298)	(39,881)
Proceeds from sales of loans and leases held-for-sale	2,001,489	966,352	372,354
Originations of loans and leases held-for-sale, net of repayments	(2,011,048)	(835,047)	(375,622)
Impairment of loan servicing rights	17,605	3,882	0
Net change in other assets	(484,298)	(263,351)	(35,154)
Net change in other liabilities	(119,586)	162,533	39,898
Other, net	(78,131)	(65,921)	(41,949)
Net cash provided by (used in) operating activities	121,106	641,757	563,630
Cash flows from investing activities
Proceeds from sales of investment securities available-for-sale	50,797	1,986,386	254,146
Proceeds from maturities of and principal collected on investment securities available-for-sale	2,404,269	735,861	169,622
Purchases of investment securities available-for-sale	(3,587,494)	(2,806,598)	(1,230,430)
Proceeds from maturities of and principal collected on investment securities held-to-maturity	37,389	17,632	15,407
Purchases of investment securities held-to-maturity	(80,533)	(6,844)	(2,188)
Redemption of Federal Home Loan Bank stock	428,016	256,021	269,002
Purchases of Federal Home Loan Bank stock	(306,000)	(370,000)	(278,000)
Proceeds from sales of loans and leases	554,532	1,985,093	903,606
Loan and lease originations and purchases, net of principal collected	(639,089)	(2,037,489)	(957,672)
Proceeds from sales of other assets	70,936	113,771	88,942
Proceeds from sales of other assets	(188,378)	(154,540)	(155,664)
Net cash acquired (paid) in business combinations	0	975,014	0
Other, net	17,626	(27,431)	20,935
Net cash provided by (used in) investing activities	(1,237,929)	666,876	(902,294)
Cash flows from financing activities
Net change in deposits	4,457,400	(901,522)	549,157
Net change in short-term borrowings	(2,051,721)	45,584	160
Proceeds from long-term borrowings	7,870,577	5,957,492	9,380,950
Payments on long-term borrowings	(8,855,775)	(5,499,669)	(9,182,536)
Payments on liabilities related to acquisition and portfolio purchase	0	(1,000)	(2,000)
Redemption of Series B preferred stock	0	0	(100,000)
Repurchases of common stock	(33,098)	(86,309)	(212,929)
Common shares sold to TCF employee benefit plans	0	0	715
Dividends paid on preferred stock	(9,975)	(9,975)	(11,588)
Dividends paid on common stock	(214,687)	(156,060)	(99,490)
Exercise of stock options	(23)	29	(997)
Payments related to tax-withholding upon conversion of share-based awards	(4,553)	(6,198)	(6,865)
Net investment by (distribution to) non-controlling interest	(9,098)	(9,691)	(10,638)
Net cash provided by (used in) financing activities	1,149,047	(667,319)	303,939
Net change in cash and due from banks	32,224	641,314	(34,725)
Cash and cash equivalents at beginning of period	1,228,371	587,057	621,782
Cash and cash equivalents at end of period	1,260,595	1,228,371	587,057
Cash paid (received) for:
Interest on deposits and borrowings	230,110	269,474	139,026
Income taxes, net	128,691	12,177	(26,308)
Noncash activities:
Transfer of loans and leases to other assets	45,394	88,716	105,247
Transfer of loans and leases from held-for-investment to held-for-sale, net	$ 448,721	$ 2,184,134	$ 848,941