Derivatives and Hedging Activities - Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) (Details) - Not Designated as Hedging Instrument - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Derivative [Line Items]
Amount of gain recognized in other non-interest income	$ 0.0	$ 0.1	$ 0.0	$ 0.3
Amount of net fee income recognized in other non-interest income	0.5	0.4	1.3	0.9
Amount of net gains recognized in mortgage banking revenues	$ 0.6	$ 0.1	$ 1.0	$ 0.0