Income Taxes - Income Tax Expense Reconciliation (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Income taxes computed at the federal statutory rate	$ 296,419	$ 231,595	$ 211,124
State income taxes, net of federal income tax benefit	30,046	23,738	23,919
Excess tax benefits from equity-based compensation	(58,681)	0	0
Remeasurement of net deferred tax assets due to enactment of Tax Cut and Jobs Act	62,702	0	0
Other, net	(21,096)	(18,898)	(14,758)
Total	$ 309,390	$ 236,435	$ 220,285