Investments - Declines in Fair Value, Fixed Maturities (Details) (Debt Securities [Member], USD $) In Millions, unless otherwise specified	Sep. 30, 2013
Investment Grade [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Fair Value	$ 1,464
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Fair Value	207
Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost	1,515
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost	225
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Aggregate Losses	(51)
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Aggregate Losses	(18)
Investment Grade [Member] | One Year Or Less [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	623
Investment Grade [Member] | More Than One Year [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	80
Below Investment Grade [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Fair Value	393
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Fair Value	46
Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost	403
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost	52
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Aggregate Losses	(10)
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Aggregate Losses	$ (6)
Below Investment Grade [Member] | One Year Or Less [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	345
Below Investment Grade [Member] | More Than One Year [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Available-for-sale, Securities in Unrealized Loss Positions, Qualitative Disclosure, Number of Positions	14