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
	Mar. 31, 2018	Mar. 31, 2017
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives (Loss)/Gain	$ 141	$ 221
Interest rate swap contracts—commercial loans
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives (Loss)/Gain	115	24
Interest rate lock commitments—mortgage loans
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives (Loss)/Gain	45	233
Forward sale contracts—mortgage loans
Derivative Instruments, Gain (Loss) [Line Items]
Derivatives (Loss)/Gain	$ (19)	$ (36)