Parent Company Financial Information - Condensed Statements of Financial Condition (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Assets:
Cash and due from banks	$ 531,918	$ 491,787
Premises and equipment, net	470,131	533,138
Other assets	1,621,949	1,479,401
Total assets	47,802,487	46,651,553	$ 23,699,612
Liabilities
Long term borrowings	1,374,732
Accrued expenses and other liabilities	1,264,776	1,432,256
Total liabilities	42,113,190	40,924,312
Equity	5,670,813	5,707,015
Total liabilities and equity	47,802,487	46,651,553
TCF Financial Corporation
Assets:
Cash and due from banks	174,157	157,103	$ 91,132	$ 80,471
Premises and equipment, net	3,407	3,813
Deferred tax asset	8,888	8,536
Investment in TCF Bank	5,492,479	5,526,078
Accounts receivable from TCF Bank	23,202	25,887
Other assets	43,258	40,961
Total assets	5,745,391	5,762,378
Liabilities
Long term borrowings	19,090	19,021
Accrued expenses and other liabilities	55,488	36,342
Total liabilities	74,578	55,363
Equity	5,670,813	5,707,015
Total liabilities and equity	$ 5,745,391	$ 5,762,378