Long-Term Debt and Shareholders' Equity (Long-term Debt) (Details) - USD ($) $ in Millions	9 Months Ended
Sep. 30, 2021	Dec. 31, 2020
Debt And Equity [Abstract]
Subordinated notes	$ 593	$ 619
Senior notes	423	713
Finance lease obligations	4	4
Total	1,020	$ 1,336
Debt Instrument [Line Items]
Amount change	$ (316)
Percent change	(24.00%)
Subordinated notes
Debt Instrument [Line Items]
Amount change	$ (26)
Percent change	(4.00%)
Senior notes
Debt Instrument [Line Items]
Amount change	$ (290)
Percent change	(41.00%)
Finance lease obligations
Debt Instrument [Line Items]
Amount change	$ 0
Percent change	0.00%

Net increase or decrease in the carrying amount of the debt instrument for the period.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Present value of lessee's discounted obligation for lease payments from finance lease.

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Amount, after unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but not limited to, notes payable, bonds payable, debentures, mortgage loans and commercial paper. Excludes capital lease obligations.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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Debt And Equity

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Debt Instrument, Increase (Decrease), Net, Percentage

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