Quarterly Results Quarterly Results (Unaudited) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effect of Fourth Quarter Events [Line Items]
Net income tax expense (benefit)			$ 228,212	$ 254,323	$ 277,192
Net foreign currency gains (losses)			$ (13,315)	$ 7,955	$ 7,820
Tax Cuts and Jobs Act - Provisional
Effect of Fourth Quarter Events [Line Items]
Net income tax expense (benefit)	$ (39,268)
Egypt, Pounds
Effect of Fourth Quarter Events [Line Items]
Net foreign currency gains (losses)		$ 6,000