Income Taxes - Schedule of Reconciliation of Federal Statutory Rate to Company's Effective Tax Rate (Detail)		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Tax Disclosure [Abstract]
Federal income tax provision at statutory rate		35.00%	35.00%	35.00%
State income taxes, net of federal income tax benefit		0.40%	(15.00%)	0.30%
Foreign income tax rate differential		(28.70%)	(96.30%)	(8.60%)
Rate changes due to enacted legislation		(0.60%)	(6.70%)
Tax effect of credits		(16.10%)	(30.30%)	(1.90%)
Provision for (resolution of ) tax matters		16.90%	2.80%	(2.10%)
State benefit due to enacted legislation		(4.10%)
Effect of U.S. tax law change	[1]	53.20%
Valuation allowance		23.30%	7.10%	0.40%
Permanent differences on non-U.S. earnings				(4.40%)
Other		0.60%	3.90%	(0.90%)
Actual tax rate		79.90%	(99.50%)	17.80%

[1] Due to the TCJA which was enacted in December 2017, provisional mandatory transition tax on accumulated foreign earnings was accrued as of December 31, 2017. Our U.S. deferred tax assets and liabilities as of December 31, 2017 were re-measured from 35% to 21%.