Allowance for Loan and Lease Losses and Credit Quality Information - Modified TDR Loan Balances that Defaulted During the Period (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Loan Modifications for Borrowers with Financial Difficulties
Minimum period for loans to be delinquent to be considered in default		90 days	90 days
Defaulted TDR loan balance modified during the period	[1]	$ 9,949	$ 5,384	$ 11,516
Consumer real estate
Loan Modifications for Borrowers with Financial Difficulties
Defaulted TDR loan balance modified during the period	[1]	3,816	3,660	9,823
Consumer real estate | First mortgage lien
Loan Modifications for Borrowers with Financial Difficulties
Defaulted TDR loan balance modified during the period	[1]	3,514	3,081	8,193
Consumer real estate | Junior lien
Loan Modifications for Borrowers with Financial Difficulties
Defaulted TDR loan balance modified during the period	[1]	302	579	1,630
Commercial | Commercial business
Loan Modifications for Borrowers with Financial Difficulties
Defaulted TDR loan balance modified during the period	[1]	4,697	0	0
Leasing and equipment finance
Loan Modifications for Borrowers with Financial Difficulties
Defaulted TDR loan balance modified during the period	[1]	0	555	0
Auto finance
Loan Modifications for Borrowers with Financial Difficulties
Defaulted TDR loan balance modified during the period	[1]	$ 1,436	$ 1,169	$ 1,693

[1] The loan balances presented are not materially different than the pre-modification loan balances as TCF's loan modifications generally do not forgive principal amounts.