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, 2021	Mar. 31, 2021	Dec. 31, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	$ 10,710		$ 11,697
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(37)	$ (43)	(44)	$ (51)	$ (45)	$ 0
Debt securities, held to maturity, net carrying value	10,673		11,653
Held-to-maturity, Gross Unrealized Appreciation	670		859
Held-to-maturity, Gross Unrealized Depreciation	0		(2)
Held to maturity, at Fair Value	11,343		12,510
U.S. Treasury / Agency
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,041		1,392
Debt Securities, Held-to-maturity, Allowance for Credit Loss	0		0
Debt securities, held to maturity, net carrying value	1,041		1,392
Held-to-maturity, Gross Unrealized Appreciation	41		60
Held-to-maturity, Gross Unrealized Depreciation	0		0
Held to maturity, at Fair Value	1,082		1,452
Non-U.S.
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,285		1,295
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(5)		(7)
Debt securities, held to maturity, net carrying value	1,280		1,288
Held-to-maturity, Gross Unrealized Appreciation	86		118
Held-to-maturity, Gross Unrealized Depreciation	0		(1)
Held to maturity, at Fair Value	1,366		1,405
Corporate and asset-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	2,117		2,185
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(30)		(35)
Debt securities, held to maturity, net carrying value	2,087		2,150
Held-to-maturity, Gross Unrealized Appreciation	227		288
Held-to-maturity, Gross Unrealized Depreciation	0		0
Held to maturity, at Fair Value	2,314		2,438
Mortgage-backed securities
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	1,782		2,000
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)		(1)
Debt securities, held to maturity, net carrying value	1,781		1,999
Held-to-maturity, Gross Unrealized Appreciation	111		148
Held-to-maturity, Gross Unrealized Depreciation	0		(1)
Held to maturity, at Fair Value	1,892		2,146
Municipal
Schedule of Held-to-maturity Securities [Line Items]
Debt Securities, Held-to-maturity	4,485		4,825
Debt Securities, Held-to-maturity, Allowance for Credit Loss	(1)		(1)
Debt securities, held to maturity, net carrying value	4,484		4,824
Held-to-maturity, Gross Unrealized Appreciation	205		245
Held-to-maturity, Gross Unrealized Depreciation	0		0
Held to maturity, at Fair Value	$ 4,689		$ 5,069