Financial Instruments (Cash, Cash Equivalents and Marketable Securities Measured at Adjusted Cost, Gross Unrealized Gains, Gross Unrealized Losses, and Fair Value By Significant Investment Category) (Details) - USD ($) $ in Millions	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	$ 86,603	$ 73,141
Gross Unrealized Gains	361	346
Gross Unrealized Losses	(631)	(421)
Fair Value	86,333	73,066
Cash and Cash Equivalents	12,918	16,549	$ 18,347	$ 18,898
Marketable Securities	73,415	56,517
Cash
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	7,078	7,380
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	7,078	7,380
Cash and Cash Equivalents	7,078	7,380
Marketable Securities	0	0
Level 1
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	43,397	27,237
Gross Unrealized Gains	179	182
Gross Unrealized Losses	(215)	(48)
Fair Value	43,361	27,371
Cash and Cash Equivalents	5,396	5,881
Marketable Securities	37,965	21,490
Level 1 | Money market and other funds
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	4,783	5,623
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	4,783	5,623
Cash and Cash Equivalents	4,783	5,623
Marketable Securities	0	0
Level 1 | U.S. government notes
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	38,454	20,922
Gross Unrealized Gains	46	27
Gross Unrealized Losses	(215)	(48)
Fair Value	38,285	20,901
Cash and Cash Equivalents	613	258
Marketable Securities	37,672	20,643
Level 1 | Marketable equity securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	160	692
Gross Unrealized Gains	133	155
Gross Unrealized Losses	0	0
Fair Value	293	847
Cash and Cash Equivalents	0	0
Marketable Securities	293	847
Level 2
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	36,128	38,524
Gross Unrealized Gains	182	164
Gross Unrealized Losses	(416)	(373)
Fair Value	35,894	38,315
Cash and Cash Equivalents	444	3,288
Marketable Securities	35,450	35,027
Level 2 | Money market and other funds
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost		1,140
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		1,140
Cash and Cash Equivalents		1,140
Marketable Securities		0
Level 2 | Time deposits
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	142	3,223
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	142	3,223
Cash and Cash Equivalents	140	2,012
Marketable Securities	2	1,211
Level 2 | Mutual funds
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	204
Gross Unrealized Gains	7
Gross Unrealized Losses	0
Fair Value	211
Cash and Cash Equivalents	0
Marketable Securities	211
Level 2 | Fixed-income bond funds
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost		219
Gross Unrealized Gains		0
Gross Unrealized Losses		0
Fair Value		219
Cash and Cash Equivalents		0
Marketable Securities		219
Level 2 | U.S. government agencies
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	1,826	1,367
Gross Unrealized Gains	0	2
Gross Unrealized Losses	(11)	(3)
Fair Value	1,815	1,366
Cash and Cash Equivalents	300	0
Marketable Securities	1,515	1,366
Level 2 | Foreign government bonds
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	2,345	2,242
Gross Unrealized Gains	18	14
Gross Unrealized Losses	(7)	(23)
Fair Value	2,356	2,233
Cash and Cash Equivalents	0	0
Marketable Securities	2,356	2,233
Level 2 | Municipal securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	4,757	3,812
Gross Unrealized Gains	15	47
Gross Unrealized Losses	(65)	(4)
Fair Value	4,707	3,855
Cash and Cash Equivalents	2	0
Marketable Securities	4,705	3,855
Level 2 | Corporate debt securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	12,993	13,809
Gross Unrealized Gains	114	53
Gross Unrealized Losses	(116)	(278)
Fair Value	12,991	13,584
Cash and Cash Equivalents	2	136
Marketable Securities	12,989	13,448
Level 2 | Agency mortgage-backed securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	12,006	9,680
Gross Unrealized Gains	26	48
Gross Unrealized Losses	(216)	(57)
Fair Value	11,816	9,671
Cash and Cash Equivalents	0	0
Marketable Securities	11,816	9,671
Level 2 | Asset-backed securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	1,855	3,032
Gross Unrealized Gains	2	0
Gross Unrealized Losses	(1)	(8)
Fair Value	1,856	3,024
Cash and Cash Equivalents	0	0
Marketable Securities	$ 1,856	$ 3,024