Cash, Cash Equivalents, and Marketable Securities Summary by Major Security Type Cash Cash Equivalents and Marketable Securities Measured at Fair Value on Recurring (Details) - USD ($) $ in Millions	Sep. 30, 2016	Dec. 31, 2015
Cash, cash equivalents and marketable securities [Line Items]
Cash, Cash Equivalents, and Short-term Investments	$ 18,347	$ 19,808
Less: Restricted Cash and Cash Equivalents	(468)	(285)
Cash
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	5,730
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Cash, Cash Equivalents, and Short-term Investments	5,730	6,201
Cash, cash equivalents, and marketable securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	18,708
Gross Unrealized Gains	112
Gross Unrealized Losses	(5)
Cash, Cash Equivalents, and Short-term Investments	18,815	20,093
Level 1 Securities | Money market funds
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	8,386
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Cash, Cash Equivalents, and Short-term Investments	8,386	8,025
Level 1 Securities | Equity securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	23
Gross Unrealized Gains	106
Gross Unrealized Losses	0
Cash, Cash Equivalents, and Short-term Investments	129	15
Level 2 Securities | Foreign government and agency securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	45
Gross Unrealized Gains	1
Gross Unrealized Losses	0
Cash, Cash Equivalents, and Short-term Investments	46	49
Level 2 Securities | U.S. government and agency securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	3,695
Gross Unrealized Gains	3
Gross Unrealized Losses	(4)
Cash, Cash Equivalents, and Short-term Investments	3,694	5,167
Level 2 Securities | Corporate debt securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	587
Gross Unrealized Gains	2
Gross Unrealized Losses	0
Cash, Cash Equivalents, and Short-term Investments	589	477
Level 2 Securities | Asset-backed securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	152
Gross Unrealized Gains	0
Gross Unrealized Losses	(1)
Cash, Cash Equivalents, and Short-term Investments	151	117
Level 2 Securities | Other fixed income securities
Cash, cash equivalents and marketable securities [Line Items]
Cost or Amortized Cost	90
Gross Unrealized Gains	0
Gross Unrealized Losses	0
Cash, Cash Equivalents, and Short-term Investments	$ 90	$ 42