Investments - Declines in Fair Value, Fixed Maturities (Details) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014
Debt Securities [Member] | 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	$ 1,307
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Fair Value	285
Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost	1,321
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost	296
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Aggregate Losses	(14)
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Aggregate Losses	(11)
Debt Securities [Member] | 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	276
Debt Securities [Member] | 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	123
Debt Securities [Member] | 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	319
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Fair Value	63
Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost	325
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost	68
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Aggregate Losses	(6)
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Aggregate Losses	(5)
Debt Securities [Member] | 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	301
Debt Securities [Member] | 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	21
Equity securities [Member]
Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract]
Securities with a fair value significantly lower than cost, excluding hybrid securities	$ 0