Financial Instruments - Additional Information (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Mar. 31, 2013	Dec. 31, 2013
Amortized Cost And Fair Value Debt Securities [Abstract]
Financial instruments including money market funds maturities period	90 days
Maximum maturities period of long-term marketable securities	3 years
Minimum maturities period of long-term marketable securities	1 year
Maximum maturities period of short-term marketable securities	12 months
Minimum maturities period of short-term marketable securities	90 days
Material realized gains or losses related to sales of marketable securities	$ 0	$ 0
Total fair value of marketable securities	193
Recognize impairment charges	0	0
Investments in marketable securities	$ 0		$ 0