Derivative Instruments and Hedging Activities - Effect Of Derivatives On Interest Income (Details) - Designated as Hedging Instrument - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	$ (145)	$ 397	$ (521)	$ 1,074
Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	(127)	453	(462)	1,164
Interest Income | Fair Value Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	(18)	(56)	(59)	(90)
Interest Income | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	376	1,531	647	3,387
Interest Expense | Cash Flow Hedging
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Gain (loss) on derivative, net	$ (503)	$ (1,078)	$ (1,109)	$ (2,223)