Income Taxes - Difference Between Total Tax Expense and Amount Computed by Applying Statutory Federal Income Tax Rate (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Contingency [Line Items]
Statutory rate applied to income	$ 225,879	$ 353,259	$ 376,019
Plus state income taxes, net of Federal tax benefit	35,626	27,918	29,211
Taxation of foreign operations, net	(7,639)	(33,984)	(18,057)
U.S. tax reform - transition tax	4,875	37,132	0
Book tax basis difference in investment	(11,944)	0	0
Valuation allowance	20,505	1,273	371
Other	(1,127)	2,397	(444)
Income tax expense, total	265,138	392,511	387,100
Domestic Tax Authority [Member]
Income Tax Contingency [Line Items]
Deferred tax remeasurement	424	13,854	0
Foreign Tax Authority [Member]
Income Tax Contingency [Line Items]
Deferred tax remeasurement	$ (1,461)	$ (9,338)	$ 0