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	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Held to maturity, Amortized Cost	$ 11,896		$ 12,581
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(51)	$ (45)	0
Debt securities, held to maturity, net carrying value	11,845
Held-to-maturity, Gross Unrealized Appreciation	791		427
Held-to-maturity, Gross Unrealized Depreciation	(16)		(3)
Held-to-maturity, Fair Value	12,620		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	1,242		1,318
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0
Debt securities, held to maturity, net carrying value	1,242
Held-to-maturity, Gross Unrealized Appreciation	73		29
Held-to-maturity, Gross Unrealized Depreciation	0		0
Held-to-maturity, Fair Value	1,315		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	1,278		1,423
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(8)
Debt securities, held to maturity, net carrying value	1,270
Held-to-maturity, Gross Unrealized Appreciation	102		62
Held-to-maturity, Gross Unrealized Depreciation	(2)		0
Held-to-maturity, Fair Value	1,370		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	2,232		2,349
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(41)
Debt securities, held to maturity, net carrying value	2,191
Held-to-maturity, Gross Unrealized Appreciation	247		121
Held-to-maturity, Gross Unrealized Depreciation	(10)		(2)
Held-to-maturity, Fair Value	2,428		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	2,189		2,331
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)
Debt securities, held to maturity, net carrying value	2,188
Held-to-maturity, Gross Unrealized Appreciation	146		65
Held-to-maturity, Gross Unrealized Depreciation	(3)		0
Held-to-maturity, Fair Value	2,331		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	4,955		5,160
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)
Debt securities, held to maturity, net carrying value	4,954
Held-to-maturity, Gross Unrealized Appreciation	223		150
Held-to-maturity, Gross Unrealized Depreciation	(1)		(1)
Held-to-maturity, Fair Value	$ 5,176		5,309
Accumulated Other Comprehensive Income (Loss), Other than Temporary Impairment, Not Credit Loss, Net of Tax, Held-to-maturity, Debt Securities			$ 0