Income Taxes - Provision for Federal and State Income Taxes (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current:
Federal									$ 2,400	$ 5,113	$ 2,509
State									539	829	777
Deferred:
Federal									909	3,877	4,027
State									33	(61)	135
Provision for federal and state income taxes, total	$ 568	$ (1,533)	$ 2,046	$ 2,800	$ 2,553	$ 2,779	$ 2,292	$ 2,134	$ 3,881	$ 9,758	$ 7,448