Income Taxes - Components of Consolidated Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current:
Federal	$ 28,047	$ 20,811	$ 15,270
State	1,012	684	504
Total Current	29,059	21,495	15,774
Deferred:
Federal	1,343	(821)	(207)
State	103	(591)
Total Deferred	1,446	(1,412)	(207)
Income tax expense, Total	$ 30,505	$ 20,083	$ 15,567