Derivatives and Hedging Activities - Narrative (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($) swap	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) swap	Sep. 30, 2017 USD ($)	Dec. 31, 2017 USD ($) swap
Derivative [Line Items]
Noninterest income	$ 5,290	$ 1,630	$ 15,280	$ 12,266
Fee income	164		164
Accrued interest on derivatives, at fair value	123		123		$ 7
Currency forward contract - non-designated hedge
Derivative [Line Items]
Notional amount of derivative					$ 1,600
Interest rate products - designated
Derivative [Line Items]
Notional amount of derivative	$ 16,000		$ 16,000
Number of interest rate derivatives held | swap	21		21		2
Notional amount, obligation to return cash	$ 275,000		$ 275,000		$ 20,000
Not-designated hedge | Currency forward contract - non-designated hedge
Derivative [Line Items]
Noninterest income	$ (14)		$ (14)