Investments (Held-to-maturity credit quality indicator) (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 10,153	$ 11,697
Fixed Maturities Percent of Total Amortized cost	100.00%	100.00%
Fixed maturities held to maturity, at amortized cost, net of valuation allowance - $35 and $44 (fair value – $10,647 and $12,510)	$ 10,118	$ 11,653
U.S. Treasury and agency
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	1,213	1,392
Fixed maturities held to maturity, at amortized cost, net of valuation allowance - $35 and $44 (fair value – $10,647 and $12,510)	1,213	1,392
Debt Security, Government, Non-US [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	1,201	1,295
Fixed maturities held to maturity, at amortized cost, net of valuation allowance - $35 and $44 (fair value – $10,647 and $12,510)	1,196	1,288
Corporate securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	2,032	2,185
Fixed maturities held to maturity, at amortized cost, net of valuation allowance - $35 and $44 (fair value – $10,647 and $12,510)	2,004	2,150
Mortgage-backed securities
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	1,731	2,000
Fixed maturities held to maturity, at amortized cost, net of valuation allowance - $35 and $44 (fair value – $10,647 and $12,510)	1,730	1,999
States, municipalities, and political subdivisions
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	3,976	4,825
Fixed maturities held to maturity, at amortized cost, net of valuation allowance - $35 and $44 (fair value – $10,647 and $12,510)	3,975	4,824
Standard & Poor's, AAA Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 2,089	$ 2,511
Fixed Maturities Percent of Total Amortized cost	21.00%	22.00%
Standard & Poor's, AA Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 5,303	$ 6,193
Fixed Maturities Percent of Total Amortized cost	52.00%	53.00%
Standard & Poor's, A Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 1,964	$ 2,138
Fixed Maturities Percent of Total Amortized cost	19.00%	18.00%
Standard & Poor's, BBB Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 773	$ 826
Fixed Maturities Percent of Total Amortized cost	8.00%	7.00%
Standard & Poor's, BB Rating [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 23	$ 28
Fixed Maturities Percent of Total Amortized cost	0.00%	0.00%
Other [Member]
Debt Securities, Held-to-maturity, Credit Quality Indicator [Line Items]
Debt Securities, Held-to-maturity	$ 1	$ 1
Fixed Maturities Percent of Total Amortized cost	0.00%	0.00%