Derivative Instruments and Hedge Activities - Summary of Company's Interest Rate Derivative and Offsetting Positions (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Derivative Instruments And Hedging Activities Disclosure [Abstract]
Derivative assets fair value	$ 5,981	$ 4,317
Net amount presented in the Consolidated Statements of Financial Condition	5,981
Gross amounts not offset in the Consolidated Statements of Financial Condition
Offsetting derivative positions	(232)
Collateral posted	(5,371)
Net credit exposure	378
Derivative liabilities fair value	994	$ 559
Net amount presented in the Consolidated Statements of Financial Condition	994
Gross amounts not offset in the Consolidated Statements of Financial Condition
Offsetting derivative positions	(232)
Collateral posted	(745)
Net credit exposure	$ 17

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