Investments (Details) - USD ($) $ in Millions	Jun. 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 $44)	$ 4,432
One year through two years	2,504
Two years through three years	1,852
Three years through four years	1,163
Four years through five years	147
Five years through six years	32
Six years through seven years	3
Seven years through eight years	9
Eight years through nine years	0
Nine years through ten years	1
Ten years through eleven years	0
Eleven years through twelve years	4
Estimated Fair Value	10,147
Short-term Investments
Schedule of Available-for-sale Securities [Line Items]
Restricted cash	44	$ 29
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	4,440	2,741
Gross Unrealized Gains	1,144	1,029
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	5,583	3,769
Short-term Investments | Corporate debt securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	3,737	2,519
Gross Unrealized Gains	1	1
Gross Unrealized Losses	(1)	(1)
Estimated Fair Value	3,737	2,519
Short-term Investments | Government and agency securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	595	3
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	595	3
Short-term Investments | Equity instruments
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	8	9
Gross Unrealized Gains	1,143	1,028
Gross Unrealized Losses	0	0
Estimated Fair Value	1,151	1,037
Long-Term Investment
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	5,705	5,551
Gross Unrealized Gains	20	19
Gross Unrealized Losses	(10)	(18)
Estimated Fair Value	5,715	5,552
Long-Term Investment | Corporate debt securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	5,654	5,319
Gross Unrealized Gains	20	18
Gross Unrealized Losses	(10)	(18)
Estimated Fair Value	5,664	5,319
Long-Term Investment | Government and agency securities
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	51	232
Gross Unrealized Gains	0	1
Gross Unrealized Losses	0	0
Estimated Fair Value	51	233
Time deposits and other | Short-term Investments
Available-for-sale Securities, Gross Unrealized Gain (Loss) [Abstract]
Gross Amortized Cost	56	181
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Estimated Fair Value	$ 56	$ 181