Fair Value Measurements (details) - Changes in Level 3 (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2014	Sep. 30, 2014	Dec. 31, 2013
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	$ 300	$ 289	$ 284
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains (losses)	1	4	16
Level 3 fair value category, total unrealized investment gains (losses) reported in increases (decreases) in other comprehensive income	(1)	(1)	(1)
Level 3 fair value category purchases	74	217	180
Level 3 fair value category sales		(1)	(58)
Level 3 fair value category settlements/maturities	(13)	(73)	(83)
Gross transfers into Level 3	8	8	15
Gross transfers out of Level 3	(65)	(139)	(64)
Level 3 fair value category, ending balance	304	304	289
Fixed maturities [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	264	255	230
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains (losses)	1	3	4
Level 3 fair value category, total unrealized investment gains (losses) reported in increases (decreases) in other comprehensive income	(2)	(2)	(2)
Level 3 fair value category purchases	74	216	180
Level 3 fair value category sales		(1)	(25)
Level 3 fair value category settlements/maturities	(13)	(73)	(83)
Gross transfers into Level 3	8	8	15
Gross transfers out of Level 3	(65)	(139)	(64)
Level 3 fair value category, ending balance	267	267	255
Other investments [Member]
Changes in Level 3 fair value category [Roll Forward]
Level 3 fair value category, beginning balance	36	34	54
Level 3 fair value category, total realized and unrealized investment gains (losses) reported in net realized investment gains (losses)		1	12
Level 3 fair value category, total unrealized investment gains (losses) reported in increases (decreases) in other comprehensive income	1	1	1
Level 3 fair value category purchases		1
Level 3 fair value category sales			(33)
Level 3 fair value category, ending balance	$ 37	$ 37	$ 34