Income Taxes - Components of Income Tax Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Current:
Federal	$ 252,337	$ 284,199	$ 309,403
State	29,288	41,083	45,460
Foreign	44,896	28,593	27,602
Deferred:
Federal	71,238	26,684	28,754
State	13,663	3,857	4,225
Foreign	(18,911)	2,684	2,565
Income tax expense, total	$ 392,511	$ 387,100	$ 418,009