Fair Value Measurements (Assets and Liabilities, Measured At Fair Value Using Significant Unobservable Inputs) (Detail) - Level 3 - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022		Mar. 31, 2021
Equity Securities [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of Period, Assets	$ 77		$ 73
Transfers Into Level 3, Asset	1		0
Transfers out of Level 3, Assets	0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		0
Net Realized Gains/ (Losses), Assets	4		2
Purchases, Assets	3		3
Sales, Assets	(3)		(3)
Settlements, Assets	0		0
Other, Assets	0		0
Balance-End of Period, Assets	82		75
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	4		2
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	0		0
Short-term Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of Period, Assets	7		5
Transfers Into Level 3, Asset	0		0
Transfers out of Level 3, Assets	0
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		0
Net Realized Gains/ (Losses), Assets	0		0
Purchases, Assets	2		1
Sales, Assets	0		0
Settlements, Assets	(5)		(5)
Other, Assets	0		0
Balance-End of Period, Assets	4		1
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0		0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	0		0
Other Investments [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of Period, Assets			10
Transfers Into Level 3, Asset			0
Change in Net Unrealized Gains (Losses) included in OCI, Assets			0
Net Realized Gains/ (Losses), Assets			0
Purchases, Assets			0
Sales, Assets			0
Settlements, Assets			0
Other, Assets			0
Balance-End of Period, Assets			10
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets			0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets			0
Available-for-sale Securities [Member] | Non-U.S.
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of Period, Assets	633		546
Transfers Into Level 3, Asset	18		0
Transfers out of Level 3, Assets	(23)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(13)		8
Net Realized Gains/ (Losses), Assets	(2)		0
Purchases, Assets	43		121
Sales, Assets	(6)		(7)
Settlements, Assets	(32)		(18)
Other, Assets	0		0
Balance-End of Period, Assets	618		650
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	(2)		0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	(13)		10
Available-for-sale Securities [Member] | Corporate and asset-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of Period, Assets	2,049		1,573
Transfers Into Level 3, Asset	29		17
Transfers out of Level 3, Assets	(50)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	(22)		6
Net Realized Gains/ (Losses), Assets	0		(3)
Purchases, Assets	315		169
Sales, Assets	(27)		(25)
Settlements, Assets	(65)		(125)
Other, Assets	0		0
Balance-End of Period, Assets	2,229		1,612
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0		(3)
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	(22)		11
Available-for-sale Securities [Member] | Mortgage-backed securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance- Beginning of Period, Assets	26		60
Transfers Into Level 3, Asset	0		0
Transfers out of Level 3, Assets	(5)
Change in Net Unrealized Gains (Losses) included in OCI, Assets	0		0
Net Realized Gains/ (Losses), Assets	0		0
Purchases, Assets	0		0
Sales, Assets	0		0
Settlements, Assets	(1)		(9)
Other, Assets	0		0
Balance-End of Period, Assets	20		51
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Assets	0		0
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Assets	0		0
Guaranteed Minimum Income Benefit [Member]
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Balance - Beginning of Period, Liabilities	745	[1]	1,089	[2]
Transfers into level 3, liability	0		0
Transfers out of Level 3, Liabilities	0
Change in Net Unrealized Gains (losses) included in OCI, Liabilities	0		0
Net Realized Gains/(Losses), Liabilities	(35)	[1]	(319)	[2]
Purchases, Liabilities	0		0
Sales, Liabilities	0		0
Settlements, Liabilities	0		0
Other, Liabilities	(14)	[1]	(10)	[2]
Balance - End of Period, Liabilities	696	[1]	760	[2]
Net Realized Gains/Losses Attributable to Changes in Fair Value at the Balance Sheet Date, Liabilities	(35)	[1]	(319)	[2]
Change in Net Unrealized Gains/Losses included in OCI at the Balance Sheet Date, Liabilities	$ 0		$ 0

[1] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value.

[2] Our GLB reinsurance product meets the definition of a derivative instrument for accounting purposes and is accordingly carried at fair value.