Derivative Instruments and Hedging Activities - Amount of Gain or Loss Recognized in Income on Derivatives (Details) - Not Designated as Hedging Instruments - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives (Loss)/Gain	$ (39)	$ (25)	$ 14	$ 251
Interest rate swap contracts—commercial loans
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives (Loss)/Gain	31	9	(55)	25
Interest rate lock commitments—mortgage loans
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives (Loss)/Gain	(169)	(4)	3	216
Forward sale contracts—mortgage loans
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives (Loss)/Gain	$ 99	$ (30)	$ 66	$ 10