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Municipal Bond Guarantee Insurance - Schedule of Municipal Bond Guarantee Insured Obligations (Details) - BAM $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2023 USD ($) Contract	Dec. 31, 2022 USD ($) Contract
Guarantor Obligations [Line Items]
Contracts outstanding | Contract	13,835	13,382
Remaining weighted average contract period (in years)	10 years 9 months 18 days	10 years 9 months 18 days
Principal	$ 103,962.3	$ 99,996.9
Interest	51,414.9	48,880.6
Total debt service outstanding	155,377.2	148,877.5
Total gross unearned insurance premiums	$ 303.7	$ 298.3

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- Definition

Amount of unearned premium revenue under contracts issued by an insurance entity that provide protection to the holder of a financial obligation from a financial loss in the event of a default.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 460
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)(1)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482425/460-10-50-4

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- Definition

Remaining weighted average contract period of financial guarantee insurance contracts, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Municipal bond contracts issued and outstanding.

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