Fair Value Measurements - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015	Dec. 31, 2015
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Available for sale investments, short-term	$ 16,000,000		$ 16,000,000		$ 34,000,000
Available for sale investments, long-term	60,000,000		60,000,000		65,000,000
Gross unrealized gains	1,000,000		1,000,000		1,000,000
Gross unrealized losses	1,000,000		1,000,000		1,000,000
Net gains (losses) from foreign currency forward contracts	(20,000,000)	$ (4,000,000)	(48,000,000)	$ 15,000,000
Foreign Exchange Forward Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Notional amount of foreign currency derivatives	2,500,000,000		2,500,000,000
Recurring Basis | Foreign Exchange Forward Contracts
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Foreign currency forward contracts, Assets					$ 8,045,000
Foreign currency forward contracts, Liabilities	$ 18,760,000		$ 18,760,000