Stock Compensation - Deferred Compensation Plans (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Senior Officer, Winthrop and Directors Deferred Compensation Plans
Deferred Compensation Plans
Maximum amount of director fees and restricted stock awards that can be deferred	100.00%
Fair value of assets in the plan	$ 13.8	$ 15.7
Senior Officer, Winthrop and Directors Deferred Compensation Plans | TCF Common Stock
Deferred Compensation Plans
Fair value of assets in the plan	11.1	12.0
TCF Employees Deferred Stock Compensation Plan | TCF Common Stock
Deferred Compensation Plans
Fair value of assets in the plan	$ 6.3	$ 9.6