Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
U.S. Statutory income tax rate			35.00%	35.00%	35.00%
Tax charge	$ 27,500		$ 27,500
Estimated charges related to deemed repatriation transition tax			16,976
Estimated charges related to remeasurement of U.S. deferred tax assets and liabilities			10,450
Estimated charges related to deemed repatriation transition tax, gross			27,000
Foreign tax credits			(1,344)	$ (3,320)	$ (3,412)
Tax benefit from release of previously unrecognized tax benefits			3,500
Unremitted foreign earnings reinvested	214,900		214,900
Unrecognized tax benefits that would affect the effective tax rate if recognized	33,900		33,900	32,000	43,500
Amounts netted against related deferred tax assets	400		400	1,100	1,000
Gross unrecognized tax benefits decrease in next 12 months	5,500		5,500
Offset to deferred tax assets for unrecognized tax benefits			16,900
Estimated unrecognized tax benefits	17,000		17,000
Accrued interest and penalties related to unrecognized tax benefits	700		$ 700	500	$ 500
Deferred tax assets related to excess tax benefits for federal research and development income tax credits				2,200
Scenario, Forecast [Member]
Income Taxes [Line Items]
U.S. Statutory income tax rate		21.00%
RSU Forfeitures [Member]
Income Taxes [Line Items]
Deferred tax assets for tax benefit on cumulative effect adjustment associated with change in accounting				$ 600
Minimum [Member]
Income Taxes [Line Items]
Losses and credit expire			2022
Maximum [Member]
Income Taxes [Line Items]
Losses and credit expire			2027
U.S. federal [Member]
Income Taxes [Line Items]
Loss carryforwards	13,700		$ 13,700
Credit carryforwards	36,300		36,300
State [Member]
Income Taxes [Line Items]
Loss carryforwards	49,500		49,500
Credit carryforwards	$ 38,000		$ 38,000