Financial Instruments - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Investments Debt And Equity Securities [Abstract]
Financial instruments including money market funds maturities period	90 days		90 days
Maximum maturities period of long-term marketable securities	3 years		3 years
Minimum maturities period of long-term marketable securities	1 year		1 year
Maximum remaining maturity for short-term marketable securities	12 months		12 months
Minimum maturities of short-term marketable securities	90 days		90 days
Net (loss) gain related to forward contracts	$ (1)	$ 3
Derivative Instruments Not Designated as Hedging Instruments, Description of Terms	Our current forward contracts are not designated as hedges and have current maturities of less than 90 days