Aggregate number of common shares reserved for future issuance.

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Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Employee Incentive, Retirement, Deferred Compensation, and Career Achievement Plans (Employee Incentive Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares of common stock authorized to be granted under the existing stock incentive plan (in shares)	62,000,000
Total unrecognized compensation cost, net of forfeitures, related to outstanding stock options, restricted stock awards, and restricted stock units	$ 289
Employee stock purchase plan [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares reserved for future issuance under the ESPP (in shares)	32,000,000
Stock option plan [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Stock option plan [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Period from the date of grant in which stock options expire	10 years
Award vesting period	4 years
Stock option [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted-average period for unrecognized compensation cost, net of forfeitures, related to outstanding stock options, restricted stock awards, and restricted stock units	10 months 24 days
Restricted stock unit [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted-average period for unrecognized compensation cost, net of forfeitures, related to outstanding stock options, restricted stock awards, and restricted stock units	2 years 2 months 12 days
Total fair value of restricted stock awards vested	$ 175	$ 123	$ 166
Restricted stock unit [Member] \| Minimum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	1 year
Restricted stock unit [Member] \| Maximum [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Award vesting period	4 years
Performance Shares [Member]
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Remaining weighted-average period for unrecognized compensation cost, net of forfeitures, related to outstanding stock options, restricted stock awards, and restricted stock units	4 months 24 days