Supplemental Financial Statement Information (Components of Accumulated Other Comprehensive Income) (Details) - USD ($) $ in Millions	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Components of AOCI, net of tax
Beginning Balance	$ 139,036
Other comprehensive income (loss) before reclassifications	1,592	$ 941
Amounts reclassified from AOCI	64	(99)
Other comprehensive income (loss)	1,656	842
Ending Balance	157,100
Foreign Currency Translation Adjustments
Components of AOCI, net of tax
Beginning Balance	(2,646)	(2,047)
Other comprehensive income (loss) before reclassifications	1,457	166
Amounts reclassified from AOCI	0	0
Other comprehensive income (loss)	1,457	166
Ending Balance	(1,189)	(1,881)
Unrealized Gains (Losses) on Available-for-Sale Investments
Components of AOCI, net of tax
Beginning Balance	(179)	(86)
Other comprehensive income (loss) before reclassifications	803	627
Amounts reclassified from AOCI	98	137
Other comprehensive income (loss)	901	764
Ending Balance	722	678
Unrealized Gains (Losses) on Cash Flow Hedges
Components of AOCI, net of tax
Beginning Balance	423	259
Other comprehensive income (loss) before reclassifications	(668)	148
Amounts reclassified from AOCI	(34)	(236)
Other comprehensive income (loss)	(702)	(88)
Ending Balance	(279)	171
Total
Components of AOCI, net of tax
Beginning Balance	(2,402)	(1,874)
Ending Balance	$ (746)	$ (1,032)