Outstanding Exposure - BIG Net Par Outstanding (Details) $ in Millions	Jun. 30, 2022 USD ($) risk	Dec. 31, 2021 USD ($) risk
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, credit derivative	$ 3,301	$ 4,040
Total	232,812	236,392
BIG
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	5,327	7,293
Net par outstanding, credit derivative	59	63
Total	$ 5,386	$ 7,356
Number of risks, financial guaranty insurance | risk	250	262
Number of risks, credit derivative | risk	11	11
Number of risks | risk	261	273
BIG | BIG 1
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 1,814	$ 2,429
Net par outstanding, credit derivative	7	14
Total	$ 1,821	$ 2,443
Number of risks, financial guaranty insurance | risk	107	117
Number of risks, credit derivative | risk	1	2
Number of risks | risk	108	119
BIG | BIG 2
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 234	$ 177
Net par outstanding, credit derivative	10	4
Total	$ 244	$ 181
Number of risks, financial guaranty insurance | risk	20	16
Number of risks, credit derivative | risk	2	1
Number of risks | risk	22	17
BIG | BIG 3
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 3,279	$ 4,687
Net par outstanding, credit derivative	42	45
Total	$ 3,321	$ 4,732
Number of risks, financial guaranty insurance | risk	123	129
Number of risks, credit derivative | risk	8	8
Number of risks | risk	131	137