Investments - Declines in Fair Value, Fixed Maturities (Details) (Debt Securities [Member], USD $) In Millions, unless otherwise specified	Jun. 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	$ 1,406
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Fair Value	201
Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost	1,451
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost	216
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Aggregate Losses	(45)
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Aggregate Losses	(15)
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	606
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	71
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	391
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Fair Value	45
Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost	398
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost	51
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Aggregate Losses	(7)
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	407
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	13