Investments (Gross Unrealized Losses Related To Available-For-Sale And Held-To-Maturity Investments) (Detail) - Fixed Maturities [Member] - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Available For Sale Securities [Abstract]
Less than 12 months, fair value	$ 382	$ 371
Less than 12 months, unrealized losses	(4)	(3)
12 months or longer, fair value	94	206
12 months or longer, unrealized losses	(4)	(8)
Total available-for-sale, fair value	476	577
Total available-for-sale, unrealized losses	(8)	(11)
U S Treasury And Government [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	124	148
Less than 12 months, unrealized losses	0	(1)
12 months or longer, fair value	0	79
12 months or longer, unrealized losses	0	(1)
Total available-for-sale, fair value	124	227
Total available-for-sale, unrealized losses	0	(2)
US States And Political Subdivisions [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	1	11
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	0	15
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	1	26
Total available-for-sale, unrealized losses	0	0
Corporate Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	124	53
Less than 12 months, unrealized losses	(3)	(1)
12 months or longer, fair value	7	10
12 months or longer, unrealized losses	(1)	0
Total available-for-sale, fair value	131	63
Total available-for-sale, unrealized losses	(4)	(1)
Residential Mortgage Backed Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	57	62
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	0	7
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	57	69
Total available-for-sale, unrealized losses	0	0
Residential Mortgage Backed Non Agency [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	0	0
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	2	11
12 months or longer, unrealized losses	0	(5)
Total available-for-sale, fair value	2	11
Total available-for-sale, unrealized losses	0	(5)
Commercial Mortgage Backed Securities [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	0	5
Less than 12 months, unrealized losses	0	0
12 months or longer, fair value	5	0
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	5	5
Total available-for-sale, unrealized losses	0	0
Collateralized Debt Obligations [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	41	44
Less than 12 months, unrealized losses	(1)	0
12 months or longer, fair value	80	77
12 months or longer, unrealized losses	(3)	(2)
Total available-for-sale, fair value	121	121
Total available-for-sale, unrealized losses	(4)	(2)
Other Asset Backed [Member]
Available For Sale Securities [Abstract]
Less than 12 months, fair value	35	48
Less than 12 months, unrealized losses	0	(1)
12 months or longer, fair value	0	7
12 months or longer, unrealized losses	0	0
Total available-for-sale, fair value	35	55
Total available-for-sale, unrealized losses	$ 0	$ (1)