Investments (Details) - USD ($) $ in Millions	Sep. 30, 2015	Dec. 31, 2014
Available-for-sale Securities, Debt Maturities, Fair Value, Fiscal Year Maturity [Abstract]
One year or less (including restricted cash of $30)	$ 2,174
One year through two years	1,186
Two years through three years	1,273
Three years through four years	866
Four years through five years	115
Five years through six years	0
Six years through seven years	0
Seven years through eight years	8
Eight years through nine years	0
Nine years through ten years	1
Estimated Fair Value	5,623
Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Restricted cash	30	$ 19
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	2,183	2,702
Gross Unrealized Gains	732	1,029
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	2,914	3,730
Short-term Investments | Corporate debt securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	2,039	2,519
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	2,039	2,519
Short-term Investments | Government and agency securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	55	3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	55	3
Short-term Investments | Equity instruments
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	9	9
Gross Unrealized Gains	731	1,028
Gross Unrealized Losses	0	0
Estimated Fair Value	740	1,037
Long-Term Investment
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	3,468	5,551
Gross Unrealized Gains	15	19
Gross Unrealized Losses	(34)	(18)
Estimated Fair Value	3,449	5,552
Long-Term Investment | Corporate debt securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	3,468	5,319
Gross Unrealized Gains	15	18
Gross Unrealized Losses	(34)	(18)
Estimated Fair Value	3,449	5,319
Long-Term Investment | Government and agency securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost		232
Gross Unrealized Gains		1
Gross Unrealized Losses		0
Estimated Fair Value		233
Time deposits and other | Short-term Investments
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	50	152
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 50	$ 152