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Supplemental Financial Information (Share-Based Compensation) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended	3 Months Ended		6 Months Ended
	Mar. 31, 2019	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense		$ 245	$ 168	$ 428	$ 307
Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense		167	102	294	185
Unrecognized pretax compensation expense on nonvested awards		1,400		1,400
Stock options [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense		72	61	119	105
Unrecognized pretax compensation expense on nonvested awards		594		594
Employee stock purchase plans [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Recognized share-based compensation expense		$ 6	$ 5	$ 15	$ 17
Management Grant [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of stock options granted (in shares)	41.9
Weighted-average fair value of stock options granted (in dollars per share)	$ 7.91
Management Grant [Member] \| Restricted share units [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of restricted share units granted (in shares)	12.4
Weighted-average fair value of restricted share units granted (in dollars per share)	$ 39.88