Carrying value as of the balance sheet date of short-term borrowings using unsecured obligations issued by banks, corporations and other borrowers to investors. The maturities of these money market securities generally do not exceed 270 days.

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Debt - Short Term Borrowing and Commercial Paper Program (Details) - USD ($)	3 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2020	Apr. 30, 2020	Dec. 31, 2019
Line of Credit Facility [Line Items]
Short-term borrowings			$ 320,000,000		$ 0
Line of Credit
Line of Credit Facility [Line Items]
Short-term borrowings			0
Commercial Paper
Line of Credit Facility [Line Items]
Commercial paper, amount outstanding			$ 0
Principal Amount Issued				$ 3,500,000,000
Repayments of short-term debt	$ 1,000,000,000.0	$ 2,500,000,000