Financial Instruments - Schedule of Cash, Cash Equivalents and Marketable Securities (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013	Mar. 31, 2013	Dec. 31, 2012
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	$ 745	$ 670
Unrealized Gains
Unrealized Losses
Fair Value	745	670
Cash and cash equivalents	319	351	212	368
Short-Term Marketable Securities	142	131
Long-Term Marketable Securities	284	188
Amortized Cost, Cash	269	195
Cash	269	195
Level 1 | Money Market Funds
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	50	156
Unrealized Gains
Unrealized Losses
Fair Value	50	156
Cash and cash equivalents	50	156
Level 2
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	426	319
Unrealized Gains
Unrealized Losses
Fair Value	426	319
Short-Term Marketable Securities	142	131
Long-Term Marketable Securities	284	188
Level 2 | U.S. Agency Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	66	37
Unrealized Gains
Unrealized Losses
Fair Value	66	37
Short-Term Marketable Securities	14	14
Long-Term Marketable Securities	52	23
Level 2 | Certificates of Deposit
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	26	23
Unrealized Gains
Unrealized Losses
Fair Value	26	23
Short-Term Marketable Securities	20	16
Long-Term Marketable Securities	6	7
Level 2 | Commercial Paper
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	6	5
Unrealized Gains
Unrealized Losses
Fair Value	6	5
Short-Term Marketable Securities	6	5
Level 2 | Corporate Debt Securities
Schedule Of Available For Sale Securities [Line Items]
Amortized Cost	328	254
Unrealized Gains
Unrealized Losses
Fair Value	328	254
Short-Term Marketable Securities	102	96
Long-Term Marketable Securities	$ 226	$ 158