Debt (Schedule of Short-term Debt) (Details) - USD ($)	9 Months Ended
	Sep. 30, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Federal Home Loan Bank	$ 1,675,000,000	$ 1,900,000,000
Securities sold under agreements to repurchase	735,000,000	499,000,000
Total short-term borrowings	$ 2,410,000,000	2,399,000,000
Repurchase agreements mature	30 days
Cash collateral placed	$ 15,000,000	1,000,000
Cash collateral received	0	0
Unsecured debt
Short-term Debt [Line Items]
Federal Home Loan Bank	0	0
Securities sold under agreements to repurchase	0	0
Total short-term borrowings	0	0
Secured debt
Short-term Debt [Line Items]
Federal Home Loan Bank	1,675,000,000	1,900,000,000
Securities sold under agreements to repurchase	735,000,000	499,000,000
Total short-term borrowings	2,410,000,000	$ 2,399,000,000
Secured debt | Agency Mortgage-Backed Residential Debt Securities
Short-term Debt [Line Items]
Securities sold under agreements to repurchase	483,000,000
Secured debt | U.S. Treasury and Federal Agency Securities
Short-term Debt [Line Items]
Securities sold under agreements to repurchase	$ 252,000,000