Debt (Schedule of Short-term Debt) (Details) - USD ($) $ in Millions	Sep. 30, 2021	Dec. 31, 2020
Short-term Debt [Line Items]
Demand notes	$ 0	$ 2,136
Total short-term borrowings	0	2,136
Unsecured debt
Short-term Debt [Line Items]
Demand notes	0	2,136
Total short-term borrowings	0	2,136
Secured debt
Short-term Debt [Line Items]
Demand notes	0	0
Total short-term borrowings	$ 0	$ 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