Parent Company Financial Information - Condensed Statements of Financial Condition (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Assets [Abstract]
Cash and cash equivalents	$ 1,323,014	$ 587,057	$ 569,968	$ 621,782
Premises and equipment, net	554,194	427,534
Other assets	1,439,305	792,936
Total assets	45,692,511	23,699,612	22,904,785
Liabilities and Equity
Long term borrowings	860,482
Other liabilities	1,245,238	790,194
Total liabilities	39,999,094	21,143,352
Equity	5,670,104	2,537,801
Total liabilities and equity	45,692,511	23,699,612
TCF
Assets [Abstract]
Cash and cash equivalents	165,457	91,132	$ 81,982	$ 80,471
Premises and equipment, net	3,883	78
Deferred tax asset	13,485	2,974
Investment in TCF Bank	5,483,484	2,426,329
Accounts receivable from TCF Bank	19,849	23,780
Other assets	25,823	1,201
Total assets	5,711,981	2,545,494
Liabilities and Equity
Long term borrowings	19,005	0
Other liabilities	22,872	7,693
Total liabilities	41,877	7,693
Equity	5,670,104	2,537,801
Total liabilities and equity	$ 5,711,981	$ 2,545,494