Shareholders' Equity - Common Stock Repurchase Summary (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Class of Stock [Line Items]
Total purchase price of shares repurchased and retired	$ 9,914	$ 114	$ 17,593	$ 6,762
Common Stock
Class of Stock [Line Items]
Total number of shares repurchased and retired (in shares)	248		452
Total purchase price of shares repurchased and retired	$ 9,900		$ 17,600

Equity impact of the value of stock that has been repurchased and retired during the period. The excess of the purchase price over par value can be charged against retained earnings (once the excess is fully allocated to additional paid in capital).

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration