Outstanding Exposure - BIG Net Par Outstanding (Details) $ in Millions	Sep. 30, 2022 USD ($) risk	Dec. 31, 2021 USD ($) risk
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, credit derivative	$ 3,117	$ 4,040
Total	227,071	236,392
BIG
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	5,727	7,293
Net par outstanding, credit derivative	58	63
Total	$ 5,785	$ 7,356
Number of risks, financial guaranty insurance | risk	244	262
Number of risks, credit derivative | risk	11	11
Number of risks | risk	255	273
BIG | BIG 1
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 2,465	$ 2,429
Net par outstanding, credit derivative	6	14
Total	$ 2,471	$ 2,443
Number of risks, financial guaranty insurance | risk	110	117
Number of risks, credit derivative | risk	1	2
Number of risks | risk	111	119
BIG | BIG 2
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 187	$ 177
Net par outstanding, credit derivative	11	4
Total	$ 198	$ 181
Number of risks, financial guaranty insurance | risk	17	16
Number of risks, credit derivative | risk	2	1
Number of risks | risk	19	17
BIG | BIG 3
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 3,075	$ 4,687
Net par outstanding, credit derivative	41	45
Total	$ 3,116	$ 4,732
Number of risks, financial guaranty insurance | risk	117	129
Number of risks, credit derivative | risk	8	8
Number of risks | risk	125	137