Income Taxes - Summary of Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Current - federal	$ 6,181	$ 7,777	$ 8,471
Current - state	(33)	139	110
Deferred - federal	1,023	376	733
Income tax expense	$ 7,171	$ 8,292	$ 9,314