Other Comprehensive Income/Loss - Schedule of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	Sep. 30, 2017	Dec. 31, 2016
Net accumulated other comprehensive income:
Net unrealized gain (loss) on investment securities available-for-sale	$ (353)	$ (10,143)
Net unrealized gain (loss) on derivatives	0	(23)
Net actuarial gain (loss) on defined benefit post-retirement benefit plans	1,376	2,038
Net accumulated other comprehensive gain (loss)	$ 1,023	$ (8,128)