Income Taxes - Components of the Company's Income Tax Expense (Benefit) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Current taxes:
Federal	$ 34,003	$ 32,348	$ 28,258
State	5,308	4,595	2,709
Deferred taxes	(2,048)	(1,903)	(3,683)
Total income taxes	$ 37,263	$ 35,040	$ 27,284