Investments (Gross Unrealized Losses Related To Available-For-Sale And Held-To-Maturity Investments) (Detail) - USD ($) $ in Millions	Jun. 30, 2015	Dec. 31, 2014
Available For Sale Securities [Abstract]
Less than 12 months, fair value	$ 1,572	$ 851
Less than 12 months, unrealized losses	(30)	(2)
12 months or longer, fair value	495	1,220
12 months or longer, unrealized losses	(141)	(145)
Total available-for-sale, fair value	2,067	2,071
Total available-for-sale, unrealized losses	(171)	(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	384	373
12 months or longer, unrealized losses	(191)	(202)
Total held-to-maturity, fair value	384	373
Total held-to-maturity, unrealized losses	(191)	(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	384	373
12 months or longer, unrealized losses	(191)	(202)
Total held-to-maturity, fair value	384	373
Total held-to-maturity, unrealized losses	(191)	(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	1,568	845
Less than 12 months, unrealized losses	(30)	(2)
12 months or longer, fair value	495	1,220
12 months or longer, unrealized losses	(141)	(145)
Total available-for-sale, fair value	2,063	2,065
Total available-for-sale, unrealized losses	(171)	(147)
Fixed Maturities [Member] | U S Treasury And Government [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	109	197
Less than 12 months, unrealized losses	(1)	0
12 months or longer, fair value	50	175
12 months or longer, unrealized losses	(1)	(3)
Total available-for-sale, fair value	159	372
Total available-for-sale, unrealized losses	(2)	(3)
Fixed Maturities [Member] | US States And Political Subdivisions [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	412	60
Less than 12 months, unrealized losses	(11)	(1)
12 months or longer, fair value	60	257
12 months or longer, unrealized losses	(5)	(7)
Total available-for-sale, fair value	472	317
Total available-for-sale, unrealized losses	(16)	(8)
Fixed Maturities [Member] | Foreign Government Debt [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	68	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	68	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	482	468
Less than 12 months, unrealized losses	(12)	(1)
12 months or longer, fair value	79	251
12 months or longer, unrealized losses	(94)	(91)
Total available-for-sale, fair value	561	719
Total available-for-sale, unrealized losses	(106)	(92)
Fixed Maturities [Member] | Residential Mortgage Backed Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	323	16
Less than 12 months, unrealized losses	(4)	0
12 months or longer, fair value	191	387
12 months or longer, unrealized losses	(6)	(7)
Total available-for-sale, fair value	514	403
Total available-for-sale, unrealized losses	(10)	(7)
Fixed Maturities [Member] | Residential Mortgage Backed Non Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	7	10
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	17	19
12 months or longer, unrealized losses	(4)	(4)
Total available-for-sale, fair value	24	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	10	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	11	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	63	81
12 months or longer, unrealized losses	(21)	(21)
Total available-for-sale, fair value	63	82
Total available-for-sale, unrealized losses	(21)	(21)
Fixed Maturities [Member] | Other Asset Backed [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	157	69
Less than 12 months, unrealized losses	(1)	0
12 months or longer, fair value	34	44
12 months or longer, unrealized losses	(10)	(12)
Total available-for-sale, fair value	191	113
Total available-for-sale, unrealized losses	$ (11)	$ (12)