Investments in fixed maturity securities (Detail) - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	$ 25,173	$ 15,964
Unrealized gains on fixed maturity securities	395	510
Unrealized losses on fixed maturity securities	(440)	(40)
Fair value of fixed maturity securities	25,128	16,434
U.S. Treasury, U.S. government corporations and agencies [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	10,039	3,286
Unrealized gains on fixed maturity securities	12	22
Unrealized losses on fixed maturity securities	(249)	(5)
Fair value of fixed maturity securities	9,802	3,303
Foreign governments [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	10,454	10,998
Unrealized gains on fixed maturity securities	50	29
Unrealized losses on fixed maturity securities	(177)	(33)
Fair value of fixed maturity securities	10,327	10,994
Corporate bonds [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	1,945	1,363
Unrealized gains on fixed maturity securities	256	412
Unrealized losses on fixed maturity securities	(6)	(1)
Fair value of fixed maturity securities	2,195	1,774
Other [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	2,735	317
Unrealized gains on fixed maturity securities	77	47
Unrealized losses on fixed maturity securities	(8)	(1)
Fair value of fixed maturity securities	$ 2,804	$ 363

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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