Derivatives and Hedging Activities - Schedule of Derivative Instruments, Effect on Other Comprehensive Income (Loss) (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	$ 0.0	$ (0.5)	$ 0.0	$ (0.5)
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, before Tax	0.0	0.5	0.0	0.4
Not Designated as Hedging Instrument
Derivative [Line Items]
Amount of gain recognized in other non-interest income	0.1	0.1	0.3	0.0
Amount of net fee income recognized in other non-interest income	0.4	0.3	0.9	0.3
Amount of net gains recognized in mortgage banking revenues	$ 0.1	$ 0.3	$ 0.0	$ 0.2