Debt - Narrative (Details) - USD ($)	Sep. 30, 2021	Dec. 31, 2020
Line of Credit Facility [Line Items]
Borrowings outstanding	$ 2,895,000,000	$ 3,251,000,000
Credit Agreement \| Unsecured Revolving Credit Facility
Line of Credit Facility [Line Items]
Unsecured revolving credit agreement	5,000,000,000
Borrowings outstanding	$ 0

Reflects the total carrying amount as of the balance sheet date of debt having initial terms less than one year or the normal operating cycle, if longer.

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Name:	us-gaap_ShortTermBorrowings
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant