Medium- And Long-Term Debt (Narrative) (Details) $ in Millions	Jun. 30, 2016 USD ($)	Dec. 31, 2015 USD ($)
Debt Instrument [Line Items]
Unamortized debt issuance cost	$ 7	$ 8
Subsidiaries
Debt Instrument [Line Items]
Blanket lien on real estate-related loans securing FHLB advances	15,000
Potential FHLB borrowing capacity	4,000
Floating-rate FHLB advances \| Subsidiaries
Debt Instrument [Line Items]
Floating-rate FHLB advances	$ 2,800	$ 0
Number of notes issued	8
Weighted-average interest rate	0.4075%
Floating rate FHLB advances due March 4, 2026 \| Subsidiaries
Debt Instrument [Line Items]
Floating-rate FHLB advances	$ 1,600
Floating rate FHLB advances due May 20, 2026 \| Subsidiaries
Debt Instrument [Line Items]
Floating-rate FHLB advances	$ 1,200

Number of FHLB Advances

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Amount of advances or credit lines available from the Federal Home Loan Bank (FHLB).

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
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Including both current and noncurrent portions, Federal Home Loan Bank borrowings initially due beyond one year or beyond the normal operating cycle if longer.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
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Weighted average interest rate of long-term debt outstanding.

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The carrying amount, as of the date of the latest financial statement presented, of loans receivable which are owned but transferred to serve as collateral for the payment of FHLB debt obligations, and for which the transferee is not permitted to sell or re-pledge them to an unrelated party.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

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