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	Mar. 31, 2017	Dec. 31, 2016	Mar. 31, 2016	Dec. 31, 2015
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	$ 92,611	$ 86,603
Gross Unrealized Gains	244	361
Gross Unrealized Losses	(416)	(631)
Fair Value	92,439	86,333
Cash and Cash Equivalents	18,132	12,918	$ 15,111	$ 16,549
Marketable Securities	74,307	73,415
Cash
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	7,217	7,078
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	7,217	7,078
Cash and Cash Equivalents	7,217	7,078
Marketable Securities	0	0
Level 1
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	51,586	43,397
Gross Unrealized Gains	150	179
Gross Unrealized Losses	(158)	(215)
Fair Value	51,578	43,361
Cash and Cash Equivalents	10,160	5,396
Marketable Securities	41,418	37,965
Level 1 | Money market and other funds
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	4,454	4,783
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	4,454	4,783
Cash and Cash Equivalents	4,454	4,783
Marketable Securities	0	0
Level 1 | U.S. government notes
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	46,931	38,454
Gross Unrealized Gains	34	46
Gross Unrealized Losses	(158)	(215)
Fair Value	46,807	38,285
Cash and Cash Equivalents	5,706	613
Marketable Securities	41,101	37,672
Level 1 | Marketable equity securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	201	160
Gross Unrealized Gains	116	133
Gross Unrealized Losses	0	0
Fair Value	317	293
Cash and Cash Equivalents	0	0
Marketable Securities	317	293
Level 2
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	33,808	36,128
Gross Unrealized Gains	94	182
Gross Unrealized Losses	(258)	(416)
Fair Value	33,644	35,894
Cash and Cash Equivalents	755	444
Marketable Securities	32,889	35,450
Level 2 | Time deposits
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	54	142
Gross Unrealized Gains	0	0
Gross Unrealized Losses	0	0
Fair Value	54	142
Cash and Cash Equivalents	52	140
Marketable Securities	2	2
Level 2 | Mutual funds
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	233	204
Gross Unrealized Gains	8	7
Gross Unrealized Losses	0	0
Fair Value	241	211
Cash and Cash Equivalents	0	0
Marketable Securities	241	211
Level 2 | U.S. government agencies
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	2,029	1,826
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(5)	(11)
Fair Value	2,024	1,815
Cash and Cash Equivalents	649	300
Marketable Securities	1,375	1,515
Level 2 | Foreign government bonds
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	2,409	2,345
Gross Unrealized Gains	16	18
Gross Unrealized Losses	(5)	(7)
Fair Value	2,420	2,356
Cash and Cash Equivalents	0	0
Marketable Securities	2,420	2,356
Level 2 | Municipal securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	4,866	4,757
Gross Unrealized Gains	9	15
Gross Unrealized Losses	(11)	(65)
Fair Value	4,864	4,707
Cash and Cash Equivalents	24	2
Marketable Securities	4,840	4,705
Level 2 | Corporate debt securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	11,869	12,993
Gross Unrealized Gains	40	114
Gross Unrealized Losses	(33)	(116)
Fair Value	11,876	12,991
Cash and Cash Equivalents	30	2
Marketable Securities	11,846	12,989
Level 2 | Agency mortgage-backed securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	9,863	12,006
Gross Unrealized Gains	18	26
Gross Unrealized Losses	(203)	(216)
Fair Value	9,678	11,816
Cash and Cash Equivalents	0	0
Marketable Securities	9,678	11,816
Level 2 | Asset-backed securities
Cash, cash equivalents and marketable securities [Line Items]
Adjusted Cost	2,485	1,855
Gross Unrealized Gains	3	2
Gross Unrealized Losses	(1)	(1)
Fair Value	2,487	1,856
Cash and Cash Equivalents	0	0
Marketable Securities	$ 2,487	$ 1,856