Investments - Securities Accounted for As Available-for-Sale Included in Investments (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Gross unrealized gain included in accumulated other comprehensive gain/(loss)	$ 118	$ 631
Gross unrealized loss included in accumulated other comprehensive gain/(loss)	779
Net unrealized gains/(losses) included in other comprehensive income/(loss after tax	(955)	417	$ 158
Available-for-sale Securities [Member]
Net unrealized gains/(losses) included in other comprehensive income/(loss before tax	(1,280)	557
Net unrealized gains/(losses) included in other comprehensive income/(loss after tax	$ (955)	$ 417

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

+ References

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Amount, before tax and after adjustment, of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

+ References

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Amount, after tax and adjustment, of unrealized gain (loss) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and unrealized gain (loss) on investment in debt security measured at amortized cost (held-to-maturity) from transfer to available-for-sale.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
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