Investments - Declines in Fair Value, Fixed Maturities (Details) (Debt Securities [Member], USD $) In Millions, unless otherwise specified	Mar. 31, 2014
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	$ 1,389
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Fair Value	254
Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost	1,418
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost	270
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Aggregate Losses	(29)
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Aggregate Losses	(16)
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	416
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	72
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	205
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Fair Value	33
Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost	208
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost	36
Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Aggregate Losses	(3)
Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Aggregate Losses	$ (3)
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	132
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	11