Investments (Gross Unrealized Losses Related To Available-For-Sale And Held-To-Maturity Investments) (Detail) (USD $) In Millions, unless otherwise specified	Mar. 31, 2015	Dec. 31, 2014
Available For Sale Securities [Abstract]
Less than 12 months, fair value	$ 818	$ 851
Less than 12 months, unrealized losses	(4)	(2)
12 months or longer, fair value	542	1,220
12 months or longer, unrealized losses	(147)	(145)
Total available-for-sale, fair value	1,360	2,071
Total available-for-sale, unrealized losses	(151)	(147)
Held To Maturity Securities [Abstract]
Less than 12 months, fair value	0	0
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	393	373
12 months or longer, unrealized losses	(182)	(202)
Total held-to-maturity, fair value	393	373
Total held-to-maturity, unrealized losses	(182)	(202)
Corporate Obligations [Member] | Variable Interest Entity Primary Beneficiary [Member]
Held To Maturity Securities [Abstract]
Less than 12 months, fair value	0	0
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	393	373
12 months or longer, unrealized losses	(182)	(202)
Total held-to-maturity, fair value	393	373
Total held-to-maturity, unrealized losses	(182)	(202)
Perpetual Debt And Equity Securities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	4	6
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	0	0
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	4	6
Total available-for-sale, unrealized losses	0	0
Fixed Maturities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	814	845
Less than 12 months, unrealized losses	(4)	(2)
12 months or longer, fair value	542	1,220
12 months or longer, unrealized losses	(147)	(145)
Total available-for-sale, fair value	1,356	2,065
Total available-for-sale, unrealized losses	(151)	(147)
Fixed Maturities [Member] | U S Treasury And Government [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	77	197
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	50	175
12 months or longer, unrealized losses	(1)	(3)
Total available-for-sale, fair value	127	372
Total available-for-sale, unrealized losses	(1)	(3)
Fixed Maturities [Member] | US States And Political Subdivisions [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	133	60
Less than 12 months, unrealized losses	(1)	(1)
12 months or longer, fair value	73	257
12 months or longer, unrealized losses	(3)	(7)
Total available-for-sale, fair value	206	317
Total available-for-sale, unrealized losses	(4)	(8)
Fixed Maturities [Member] | Foreign Government Debt [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	22	20
Less than 12 months, unrealized losses	(1)	0
12 months or longer, fair value	0	0
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	22	20
Total available-for-sale, unrealized losses	(1)	0
Fixed Maturities [Member] | Corporate Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	363	468
Less than 12 months, unrealized losses	(1)	(1)
12 months or longer, fair value	94	251
12 months or longer, unrealized losses	(102)	(91)
Total available-for-sale, fair value	457	719
Total available-for-sale, unrealized losses	(103)	(92)
Fixed Maturities [Member] | Residential Mortgage Backed Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	154	16
Less than 12 months, unrealized losses	(1)	0
12 months or longer, fair value	205	387
12 months or longer, unrealized losses	(3)	(7)
Total available-for-sale, fair value	359	403
Total available-for-sale, unrealized losses	(4)	(7)
Fixed Maturities [Member] | Residential Mortgage Backed Non Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	8	10
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	18	19
12 months or longer, unrealized losses	(4)	(4)
Total available-for-sale, fair value	26	29
Total available-for-sale, unrealized losses	(4)	(4)
Fixed Maturities [Member] | Commercial Mortgage Backed Securities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	2	4
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	1	6
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	3	10
Total available-for-sale, unrealized losses	0	0
Fixed Maturities [Member] | Collateralized Debt Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	0	1
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	69	81
12 months or longer, unrealized losses	(22)	(21)
Total available-for-sale, fair value	69	82
Total available-for-sale, unrealized losses	(22)	(21)
Fixed Maturities [Member] | Other Asset Backed [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	55	69
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	32	44
12 months or longer, unrealized losses	(12)	(12)
Total available-for-sale, fair value	87	113
Total available-for-sale, unrealized losses	$ (12)	$ (12)