Fair Values of Assets and Liabilities - Losses Realized on Assets Measured on Non-Recurring Basis (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Fair Value Disclosures [Abstract]
Impaired loans	$ (238)	$ (6,991)	$ (1,278)	$ (14,576)
Other real estate owned	(1,094)	(245)	(1,125)	(258)
Total losses	$ (1,332)	$ (7,236)	$ (2,403)	$ (14,834)