Investments (Narrative) (Details) (USD $) In Millions, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Dec. 31, 2013
Increase (decrease) in gross AFS securities unrealized losses	$ (876)
Number of partnerships in alternative investment portfolio	152	121
Alternative investments as a percentage of overall invested assets	1.00%
Investment commitments	1,100
Investment commitments for limited partnerships	525
Investment commitments for private placements	282
Investment commitments for mortgage loans on real estate	316
California and Texas [Member]
Largest mortgage loan concentration in geographic region	23.00%	9.00%
Federal Home Loan Mortgage Corporation
Fair value	2,400	2,600
Concentration risk, percentage	2.00%	3.00%
Fannie Mae
Fair value	1,400	1,700
Concentration risk, percentage	1.00%	2.00%
Electric Industry [Member]
Fair value	9,700	8,700
Concentration risk, percentage	10.00%	9.00%
Banking Industry [Member]
Fair value	5,000	5,000
Concentration risk, percentage	5.00%	5.00%
Corporate Bonds [Member]
Percentage of fair value rated as investment grade	95.00%	96.00%
Amortized cost of portfolio rated below investment grade	3,500	3,000
Fair value of portfolio rated below investment grade	3,500	2,900
CDOs [Member]
Percentage of fair value rated as investment grade	96.00%	94.00%
Amortized cost of portfolio rated below investment grade	12	16
Fair value of portfolio rated below investment grade	$ 12	$ 13
MBS [Member]
Projected default rate on existing delinquencies on MBS (low end of range)	10.00%
Projected default rate on existing delinquencies on MBS (high end of range)	100.00%
Severity of second lien loans	100.00%
Severity of first lien loans	30.00%