Earnings Per Share - Share Repurchases (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Earnings Per Share [Abstract]
Shares Repurchased (in shares)	6	9
Cost of Shares	$ 551	$ 577

Number of shares that have been repurchased and retired during the period.

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Name:	us-gaap_StockRepurchasedAndRetiredDuringPeriodShares
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration