Fair Value Measurements (details) - Changes in Level 3 (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	$ 289	$ 284
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	4	16
Level 3 fair value category, total unrealized investment gains (losses) reported in increases (decreases) in other comprehensive income	(1)	(1)
Level 3 fair value category purchases	233	180
Level 3 fair value category sales	(2)	(58)
Level 3 fair value category settlements/maturities	(90)	(83)
Gross transfers into Level 3	18	15
Gross transfers out of Level 3	(183)	(64)
Level 3 fair value category, ending balance	268	289
Fixed maturities [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	255	230
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	3	4
Level 3 fair value category, total unrealized investment gains (losses) reported in increases (decreases) in other comprehensive income	(2)	(2)
Level 3 fair value category purchases	232	180
Level 3 fair value category sales	(1)	(25)
Level 3 fair value category settlements/maturities	(90)	(83)
Gross transfers into Level 3	18	15
Gross transfers out of Level 3	(183)	(64)
Level 3 fair value category, ending balance	232	255
Other investments [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	34	54
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains	1	12
Level 3 fair value category, total unrealized investment gains (losses) reported in increases (decreases) in other comprehensive income	1	1
Level 3 fair value category purchases	1
Level 3 fair value category sales	(1)	(33)
Level 3 fair value category, ending balance	$ 36	$ 34

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Amount of gain (loss) recognized in the income statement for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of gain (loss) recognized in other comprehensive income (loss) for financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of purchases of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of sale of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of settlement of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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Amount of transfer of financial instrument classified as an asset into level 3 of the fair value hierarchy.

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Amount of transfers of financial instrument classified as an asset out of level 3 of the fair value hierarchy.

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Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing.

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