Derivatives - Narrative (Details) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Derivative [Line Items]
Termination value of derivatives in net liability position	$ 1.2
Hedged Loans	530.9	$ 522.7
Cumulative fair value hedge adjustment	3.0	13.2
Interest Rate Lock Commitments [Member]
Derivative [Line Items]
Notional amount	96.9
Interest Rate Lock Commitments Notional Amount Member
Derivative [Line Items]
Notional amount		50.1
Forward Contract Notional [Member]
Derivative [Line Items]
Notional amount	118.6	77.6
Designated as Hedging Instrument [Member] | Interest rate swap derivatives [Member]
Derivative [Line Items]
Notional amount	471.8	473.4
Not Designated as Hedging Instrument, Economic Hedge [Member] | Interest rate swap derivatives [Member]
Derivative [Line Items]
Notional amount	$ 486.4	$ 206.8