Income Taxes - Summary of Reconciliation Between Income Taxes and Effective Income Tax Provision (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Provision at federal statutory rate	$ 31,422	$ 26,222	$ 30,087
State income taxes, net	2,545	2,418	2,229
Tax Cuts and Jobs Act benefit	(33,910)
Nondeductible business expenses (benefits)	(913)	462	696
Tax credits	(190)	(1,278)	(1,532)
Other, net	(332)	(929)	(533)
Total income tax provision	$ (1,378)	$ 26,895	$ 30,947