Outstanding Exposure - BIG Net Par Outstanding (Details) $ in Millions	Dec. 31, 2022 USD ($) risk	Dec. 31, 2021 USD ($) risk
Schedule of Insured Financial Obligations [Line Items]
Credit derivative, net par outstanding	$ 3,203	$ 4,040
Total net par outstanding	$ 233,258	236,392
Number of Risks | risk	7,583
BIG
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 5,835	7,293
Credit derivative, net par outstanding	57	63
Total net par outstanding	$ 5,892	$ 7,356
Number of risks, financial guaranty insurance | risk	247	262
Number of risks, credit derivative | risk	13	11
Number of Risks | risk	260	273
BIG | BIG 1
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 3,357	$ 2,429
Credit derivative, net par outstanding	6	14
Total net par outstanding	$ 3,363	$ 2,443
Number of risks, financial guaranty insurance | risk	122	117
Number of risks, credit derivative | risk	1	2
Number of Risks | risk	123	119
BIG | BIG 2
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 171	$ 177
Credit derivative, net par outstanding	10	4
Total net par outstanding	$ 181	$ 181
Number of risks, financial guaranty insurance | risk	14	16
Number of risks, credit derivative | risk	2	1
Number of Risks | risk	16	17
BIG | BIG 3
Schedule of Insured Financial Obligations [Line Items]
Net par outstanding, financial guaranty insurance	$ 2,307	$ 4,687
Credit derivative, net par outstanding	41	45
Total net par outstanding	$ 2,348	$ 4,732
Number of risks, financial guaranty insurance | risk	111	129
Number of risks, credit derivative | risk	10	8
Number of Risks | risk	121	137