Derivatives - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Derivative [Line Items]
Deferred net gains (loss) on derivatives	$ (7.8)
Cash Flow Hedges
Derivative [Line Items]
Maximum period for hedging transactions	7 years
Interest-bearing Deposits in Banks
Derivative [Line Items]
Cash or securities pledged as collateral	$ 25.3	$ 20.1