Investments in fixed maturity securities (Detail) - USD ($) $ in Millions	Sep. 30, 2022	Dec. 31, 2021
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	$ 18,845	$ 15,964
Unrealized gains on fixed maturity securities	240	510
Unrealized losses on fixed maturity securities	(483)	(40)
Fair value of fixed maturity securities	18,602	16,434
U.S. Treasury, U.S. government corporations and agencies [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	9,039	3,286
Unrealized gains on fixed maturity securities	4	22
Unrealized losses on fixed maturity securities	(268)	(5)
Fair value of fixed maturity securities	8,775	3,303
Foreign governments [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	8,701	10,998
Unrealized gains on fixed maturity securities	9	29
Unrealized losses on fixed maturity securities	(205)	(33)
Fair value of fixed maturity securities	8,505	10,994
Corporate bonds [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	830	1,363
Unrealized gains on fixed maturity securities	205	412
Unrealized losses on fixed maturity securities	(6)	(1)
Fair value of fixed maturity securities	1,029	1,774
Other [Member]
Summary of Investment Holdings [Line Items]
Amortized cost of fixed maturity securities	275	317
Unrealized gains on fixed maturity securities	22	47
Unrealized losses on fixed maturity securities	(4)	(1)
Fair value of fixed maturity securities	$ 293	$ 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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