Income Taxes - Reconciliation of Provision for Income Taxes at US Federal Statutory Rate to Provision in Statements of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Tax Disclosure [Abstract]
(Benefit) provision at U.S. federal statutory rate			$ (87,592)	$ (175,436)	$ 140,715
U.S. valuation allowance			64,907	558,976	0
Foreign earnings taxed at different rates, including foreign losses without benefit			103,231	266,807	(43,010)
U.S. Tax Act			3,709	(107,049)	0
State and local taxes, net of U.S. federal (expense) benefit			(2,028)	2,254	3,319
Adjustments to previously accrued taxes			6,621	5,159	(12,537)
Change in indefinite reinvestment assertion			14,566	0	0
Other			12,782	2,623	647
Provision for income taxes	$ 777,308	$ 728,835	116,196	$ 553,334	$ 89,134
Tax credit expirations			$ 8,100