Loans - Schedule of Changes in the Accretable Yield for Loans Acquired (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Debt Securities, Accretable Yield Movement Schedule [Roll Forward]
Beginning Balance	$ 7.3	$ 6.8
Accretion income	(0.7)	(0.6)
Reductions due to exit events	(0.2)	(0.6)
Reclassifications from nonaccretable differences	0.8	0.8
Ending Balance	7.2	6.4
Interest Income on Non-Accrual Loans if Accrued	$ 0.8	$ 0.9