Investments (Schedule Of Amortized Cost And Fair Value Of HTM Fixed Maturities And Related OTTI Recognized In Accumulated Other Comprehensive Income) (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	$ 11,696		$ 12,581
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(45)	$ (51)	0
Debt securities, held to maturity, net carrying value	11,651
Held-to-maturity, Gross Unrealized Appreciation	831		427
Held-to-maturity, Gross Unrealized Depreciation	(9)		(3)
Held-to-maturity, Fair Value	12,473		13,005
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities			0
U.S. Treasury / Agency
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	1,240		1,318
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Debt securities, held to maturity, net carrying value	1,240
Held-to-maturity, Gross Unrealized Appreciation	69		29
Held-to-maturity, Gross Unrealized Depreciation	0		0
Held-to-maturity, Fair Value	1,309		1,347
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities			0
Non-U.S.
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	1,273		1,423
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(7)
Debt securities, held to maturity, net carrying value	1,266
Held-to-maturity, Gross Unrealized Appreciation	109		62
Held-to-maturity, Gross Unrealized Depreciation	(1)		0
Held-to-maturity, Fair Value	1,374		1,485
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities			0
Corporate and asset-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	2,204		2,349
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(36)
Debt securities, held to maturity, net carrying value	2,168
Held-to-maturity, Gross Unrealized Appreciation	252		121
Held-to-maturity, Gross Unrealized Depreciation	(6)		(2)
Held-to-maturity, Fair Value	2,414		2,468
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities			0
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	2,104		2,331
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)
Debt securities, held to maturity, net carrying value	2,103
Held-to-maturity, Gross Unrealized Appreciation	152		65
Held-to-maturity, Gross Unrealized Depreciation	(2)		0
Held-to-maturity, Fair Value	2,253		2,396
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities			0
Municipal
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	4,875		5,160
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)
Debt securities, held to maturity, net carrying value	4,874
Held-to-maturity, Gross Unrealized Appreciation	249		150
Held-to-maturity, Gross Unrealized Depreciation	0		(1)
Held-to-maturity, Fair Value	$ 5,123		5,309
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities			$ 0