Equity Activity - AOCI Rollforward (Details) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Accumulated Other Comprehensive Income (Loss) (net of tax)
Balance at the Beginning of the Period				$ 17,725	$ 18,392
Other comprehensive income/(loss)				1,194	1,877
Balance at the End of the Period		$ 19,918	$ 19,757	19,918	19,757
Accumulated Other Comprehensive Income/(Loss)
Accumulated Other Comprehensive Income (Loss) (net of tax)
Balance at the Beginning of the Period				(26,592)	(29,398)
Other comprehensive income before reclassifications				(695)	721
Amount reclassified from accumulated other comprehensive income				1,889	1,155
Other comprehensive income/(loss)		470	669	1,194	1,877
Balance at the End of the Period		(27,820)	(27,521)	(27,820)	(27,521)
Accumulated Other Comprehensive Income/(Loss) | Accounting Standards Updates 2016-01 (Financial Instruments), 2017-12 (Hedging) and 2018-02 (Stranded Tax Effects)
Accumulated Other Comprehensive Income (Loss) (net of tax)
Cumulative Effect Of Prospective Application Of New Accounting Principle, Net Of Tax	[1]			(2,422)
Net Unrealized Gains/(Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss) (net of tax)
Balance at the Beginning of the Period				35	319
Other comprehensive income before reclassifications		(35)	(50)	(95)	(146)
Amount reclassified from accumulated other comprehensive income				305	(219)
Other comprehensive income/(loss)		(14)	(94)	210	(365)
Balance at the End of the Period		250	(46)	250	(46)
Net Unrealized Gains/(Losses) on Cash Flow Hedges | Accounting Standards Updates 2016-01 (Financial Instruments), 2017-12 (Hedging) and 2018-02 (Stranded Tax Effects)
Accumulated Other Comprehensive Income (Loss) (net of tax)
Cumulative Effect Of Prospective Application Of New Accounting Principle, Net Of Tax				5
Foreign Currency Translation Adjustments
Accumulated Other Comprehensive Income (Loss) (net of tax)
Balance at the Beginning of the Period				(2,834)	(3,603)
Other comprehensive income before reclassifications				(663)	794
Other comprehensive income/(loss)		(44)	284	(663)	794
Balance at the End of the Period		(3,451)	(2,809)	(3,451)	(2,809)
Foreign Currency Translation Adjustments | Accounting Standards Updates 2016-01 (Financial Instruments), 2017-12 (Hedging) and 2018-02 (Stranded Tax Effects)
Accumulated Other Comprehensive Income (Loss) (net of tax)
Cumulative Effect Of Prospective Application Of New Accounting Principle, Net Of Tax				46
Net Change Retirement-Related Benefit Plans
Accumulated Other Comprehensive Income (Loss) (net of tax)
Balance at the Beginning of the Period				(23,796)	(26,116)
Other comprehensive income before reclassifications				65	72
Amount reclassified from accumulated other comprehensive income				1,584	1,374
Other comprehensive income/(loss)		527	479	1,648	1,446
Balance at the End of the Period		(24,618)	(24,670)	(24,618)	(24,670)
Net Change Retirement-Related Benefit Plans | Accounting Standards Updates 2016-01 (Financial Instruments), 2017-12 (Hedging) and 2018-02 (Stranded Tax Effects)
Accumulated Other Comprehensive Income (Loss) (net of tax)
Cumulative Effect Of Prospective Application Of New Accounting Principle, Net Of Tax				(2,471)
Net Unrealized Gains/(Losses) on Available-For-Sale Securities
Accumulated Other Comprehensive Income (Loss) (net of tax)
Balance at the Beginning of the Period				3	2
Other comprehensive income before reclassifications		0	0	(1)	1
Amount reclassified from accumulated other comprehensive income					0
Other comprehensive income/(loss)		0	(1)	(1)	2
Balance at the End of the Period		$ 0	$ 4	0	$ 4
Net Unrealized Gains/(Losses) on Available-For-Sale Securities | Accounting Standards Updates 2016-01 (Financial Instruments), 2017-12 (Hedging) and 2018-02 (Stranded Tax Effects)
Accumulated Other Comprehensive Income (Loss) (net of tax)
Cumulative Effect Of Prospective Application Of New Accounting Principle, Net Of Tax				$ (2)

[1] Reflects the adoption of the FASB guidance on stranded tax effects, hedging and financial instruments. Refer to note 2, "Accounting Changes".