Contracts Accounted for as Credit Derivatives - Distribution of Credit Derivative Net Par Outstanding by Internal Rating (Details) - USD ($) $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2021
Credit Derivatives
Net Par Outstanding	$ 3,301	$ 4,040
BIG
Credit Derivatives
Net Par Outstanding	59	63
Credit Concentration Risk | Derivative, Aggregate Notional Amount
Credit Derivatives
Net Par Outstanding	$ 3,301	$ 4,040
Percentage of installment premiums denominated in currencies other than the U.S. dollar	100.00%	100.00%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | AAA
Credit Derivatives
Net Par Outstanding	$ 1,317	$ 1,503
Percentage of installment premiums denominated in currencies other than the U.S. dollar	39.90%	37.20%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | AA
Credit Derivatives
Net Par Outstanding	$ 1,116	$ 1,283
Percentage of installment premiums denominated in currencies other than the U.S. dollar	33.80%	31.80%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | A
Credit Derivatives
Net Par Outstanding	$ 329	$ 514
Percentage of installment premiums denominated in currencies other than the U.S. dollar	10.00%	12.70%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | BBB
Credit Derivatives
Net Par Outstanding	$ 480	$ 677
Percentage of installment premiums denominated in currencies other than the U.S. dollar	14.50%	16.70%
Credit Concentration Risk | Derivative, Aggregate Notional Amount | BIG
Credit Derivatives
Net Par Outstanding	$ 59	$ 63
Percentage of installment premiums denominated in currencies other than the U.S. dollar	1.80%	1.60%