Supplemental Financial Statement Information (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	$ 201,442	$ 177,628	$ 152,502
Other comprehensive income (loss) before reclassifications	2,531	1,528	(429)
Amounts excluded from the assessment of hedge effectiveness recorded in AOCI	(37)	(14)	26
Amounts reclassified from AOCI	(629)	(410)	(813)
Other comprehensive income (loss)	1,865	1,104	(1,216)
Ending Balance	222,544	201,442	177,628
Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		(34)	(697)
Ending Balance			(34)
Foreign Currency Translation Adjustments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(2,003)	(1,884)	(1,103)
Other comprehensive income (loss) before reclassifications	1,139	(119)	(781)
Amounts excluded from the assessment of hedge effectiveness recorded in AOCI	0	0	0
Amounts reclassified from AOCI	0	0	0
Other comprehensive income (loss)	1,139	(119)	(781)
Ending Balance	(864)	(2,003)	(1,884)
Foreign Currency Translation Adjustments | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		0	0
Ending Balance			0
Unrealized Gains (Losses) on Available-for-Sale Investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	812	(688)	233
Other comprehensive income (loss) before reclassifications	1,313	1,611	88
Amounts excluded from the assessment of hedge effectiveness recorded in AOCI	0	0	0
Amounts reclassified from AOCI	(513)	(111)	(911)
Other comprehensive income (loss)	800	1,500	(823)
Ending Balance	1,612	812	(688)
Unrealized Gains (Losses) on Available-for-Sale Investments | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		0	(98)
Ending Balance			0
Unrealized Gains (Losses) on Cash Flow Hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(41)	266	(122)
Other comprehensive income (loss) before reclassifications	79	36	264
Amounts excluded from the assessment of hedge effectiveness recorded in AOCI	(37)	(14)	26
Amounts reclassified from AOCI	(116)	(299)	98
Other comprehensive income (loss)	(74)	(277)	388
Ending Balance	(115)	(41)	266
Unrealized Gains (Losses) on Cash Flow Hedges | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		(30)	0
Ending Balance			(30)
Accumulated Other Comprehensive Income (Loss)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance	(1,232)	(2,306)	(992)
Ending Balance	$ 633	(1,232)	(2,306)
Accumulated Other Comprehensive Income (Loss) | Cumulative Effect, Period of Adoption, Adjustment
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning Balance		$ (30)	(98)
Ending Balance			$ (30)