Equity Activity - AOCI Rollforward (Details) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 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)				724	1,208
Balance at the End of the Period		$ 18,648	$ 18,544	18,648	18,544
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				(681)	486
Amount reclassified from accumulated other comprehensive income				1,405	723
Other comprehensive income/(loss)		294	520	724	1,208
Balance at the End of the Period		(28,290)	(28,189)	(28,290)	(28,189)
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		(111)	(71)	(60)	(96)
Amount reclassified from accumulated other comprehensive income				284	(175)
Other comprehensive income/(loss)		214	(183)	224	(271)
Balance at the End of the Period		264	47	264	47
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				(620)	510
Amount reclassified from accumulated other comprehensive income				0	0
Other comprehensive income/(loss)		(505)	240	(620)	510
Balance at the End of the Period		(3,408)	(3,093)	(3,408)	(3,093)
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				64	70
Amount reclassified from accumulated other comprehensive income				1,057	897
Other comprehensive income/(loss)		584	461	1,121	967
Balance at the End of the Period		(25,146)	(25,148)	(25,146)	(25,148)
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	2	(1)	2
Amount reclassified from accumulated other comprehensive income				0	1
Other comprehensive income/(loss)		0	2	(1)	2
Balance at the End of the Period		$ 0	$ 5	0	$ 5
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".