Investments in fixed maturity securities (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	$ 22,565	$ 25,173
Unrealized gains on fixed maturity securities	343	395
Unrealized losses on fixed maturity securities	(342)	(440)
Fair value of fixed maturity securities	22,566	25,128
U.S. Treasury, U.S. government corporations and agencies [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	9,588	10,039
Unrealized gains on fixed maturity securities	8	12
Unrealized losses on fixed maturity securities	(191)	(249)
Fair value of fixed maturity securities	9,405	9,802
Foreign governments [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	11,184	10,454
Unrealized gains on fixed maturity securities	48	50
Unrealized losses on fixed maturity securities	(144)	(177)
Fair value of fixed maturity securities	11,088	10,327
Corporate bonds [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	1,532	1,945
Unrealized gains on fixed maturity securities	263	256
Unrealized losses on fixed maturity securities	(4)	(6)
Fair value of fixed maturity securities	1,791	2,195
Other [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	261	2,735
Unrealized gains on fixed maturity securities	24	77
Unrealized losses on fixed maturity securities	(3)	(8)
Fair value of fixed maturity securities	$ 282	$ 2,804

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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