Derivatives - (Narrative) (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Notional amount	$ 131.4	$ 9.0
Termination value of derivatives in net liability position	3.3
Collateral Already Posted, Aggregate Fair Value	0.2
Hedged Loans	507.8
Cumulative fair value hedge adjusmtnet	(20.5)
Interest Rate Lock Commitments Notional Amount Member
Derivative [Line Items]
Notional amount		8.0
Designated as Hedging Instrument [Member] | Interest rate swap derivatives [Member]
Derivative [Line Items]
Notional amount	462.9	417.7
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest rate swap derivatives [Member]
Derivative [Line Items]
Notional amount	$ 184.0	$ 202.2