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		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Derivative [Line Items]
Amount of gain recognized in other non-interest income	$ 0.0	$ 0.1	$ 0.0	$ 0.4
Amount of net fee income recognized in other non-interest income	0.5	0.0	1.8	0.9
Amount of net gains recognized in mortgage banking revenues	$ 0.4	$ 0.0	$ 1.5	$ 0.0