Income Taxes - Reconciliation of Reserve for Uncertain Tax Positions, Excluding Interest and Penalties (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross balance at January 1,	$ 159,826	$ 169,687	$ 108,812
Additions based on tax positions related to current year	14,187	15,665	31,022
Additions for tax positions of prior years	1,284	18,662	47,561
Reductions for tax positions of prior years	(860)	(43,701)	(11,945)
Expiration of statutes	0	(487)	(1,237)
Tax settlements	0	0	(4,526)
Gross balance at December 31,	174,437	159,826	169,687
Related tax benefits	(1,008)	(1,008)	(14,369)
Net reserve at December 31,	173,429	158,818	$ 155,318
Non-U.S. | Libya | In 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Gross balance at January 1,	$ 40,000
Gross balance at December 31,		40,000
Related tax benefits		$ (13,000)