Income Taxes - Components of Income Taxes (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Current income taxes, Federal	$ 303,514	$ 147,406	$ 82,926
Current income taxes, State	19,234	10,725	8,051
Current income taxes, Foreign	78,354	61,084	51,970
Total current	401,102	219,215	142,947
Deferred income taxes, Federal	(255,188)	(18,723)	36,723
Deferred income taxes, State	276	1,608	1,525
Deferred income taxes, Foreign	7,200	(11,566)	(7,622)
Total deferred	(247,712)	(28,681)	30,626
Total provision	$ 153,390	$ 190,534	$ 173,573