Income Tax - Reconciliation of U.S. Statutory Income Tax Rate to Effective Income Tax Rate (Detail) - USD ($) $ in Thousands	3 Months Ended				12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Income Tax Disclosure [Abstract]
Federal income tax expense at statutory rate					$ 45,257	$ 37,949	$ 33,064
State income tax, net of federal income tax benefit					4,807	3,715	2,867
Domestic production activities deduction					(3,947)	(466)	(1,720)
Excess tax benefits related to stock option exercises					(29,582)	0	0
Non-deductible business expenses					2,979	2,414	1,485
Other, net					(64)	(57)	(169)
Income tax expense benefit	$ 9,200	$ 989	$ 5,188	$ 9,350	$ 19,450	$ 43,555	$ 35,527