Financial Instruments - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 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)	$ (1)	$ 1
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