|
Investments - Declines in Fair Value, Fixed Maturities (Details) (USD $)
In Millions, unless otherwise specified
|
Mar. 31, 2015
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| 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 |
$ 695 |
| Available For Sale Securities, Continuous Unrealized Loss Position, Twelve Months Or Longer, Fair Value |
146 |
| Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost |
712 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost |
151 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Accumulated Losses |
(17) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Accumulated Losses |
(5) |
| 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 |
139 |
| 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 |
64 |
| 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 |
245 |
| Available For Sale Securities, Continuous Unrealized Loss Position, Twelve Months Or Longer, Fair Value |
76 |
| Available For Sale Securities, Continuous Unrealized Loss Position, One Year or Less, Amortized Cost |
262 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Amortized Cost |
84 |
| Available-for-sale Securities, Continuous Unrealized Loss Position, One Year or Less, Accumulated Losses |
(17) |
| Available-for-sale Securities, Continuous Unrealized Loss Position, More Than One Year, Accumulated Losses |
(8) |
| 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 |
143 |
| 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 |
24 |
| Equity securities [Member] |
|
| Available-for-sale Securities, Continuous Unrealized Loss Position [Abstract] |
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| Securities with a significant unrealized loss reflected in accumulated other comprehensive income |
$ 0 |