Income Taxes - Components of the Company's Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current taxes:
Federal	$ 32,348	$ 28,258	$ 23,326
State	4,595	2,709	3,682
Deferred taxes	(1,903)	(3,683)	(483)
Total income taxes	$ 35,040	$ 27,284	$ 26,525