Represents the number of securities which had unrealized losses greater than 10% of book value for 12 months or more.

No definition available.

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This item represents the excess of amortized cost basis over fair value of securities that have been in a loss position for twelve months or longer for those securities which are categorized neither as held-to-maturity nor trading securities and which have unrealized losses greater than 10% of book value.

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Long-term Purchase Commitment, Additional Authorized Amount

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Number of Investment Funds

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Number of Outside Managers Managing Investment Portfolio

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No definition available.

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- Definition

Interest, dividends, rents, ancillary and other revenues earned but not yet received by the entity on its investments.

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The total amount of cash and securities held by third party trustees pursuant to terms of debt instruments or other agreements as of the date of each statement of financial position presented, which can be used by the trustee only to pay the noncurrent portion of specified obligations.

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Fair value portion of investments accounted under the equity method.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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The minimum amount the entity agreed to spend under the long-term purchase commitment.

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Amount of cash inflow from sale of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Minimum amount to be expended to satisfy the terms of arrangements in which the entity has agreed to expend funds to procure goods or services, excluding long-term purchase commitments or unconditional purchase obligations.

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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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Investments and Cash - Narrative (Details)	1 Months Ended	3 Months Ended		6 Months Ended		12 Months Ended
Investments and Cash - Narrative (Details)	Feb. 28, 2017 USD ($)	Jun. 30, 2020 USD ($) Security Investment_Funds	Jun. 30, 2019 USD ($)	Jun. 30, 2020 USD ($) Security manager Investment_Funds	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($) Security
Schedule of Investments [Line Items]
Accrued investment income		$ 75,000,000		$ 75,000,000		$ 79,000,000
Proceeds from sale of fixed-maturity securities available-for-sale		$ 404,000,000	$ 443,000,000	$ 490,000,000	$ 914,000,000
Number of outside managers managing investment portfolio \| manager				6
Number of securities with unrealized losses greater than 10% of book value for 12 months or more \| Security		25		25		19
Total unrealized losses for securities having losses greater than 10% of book value for 12 months or more		$ 18,000,000		$ 18,000,000		$ 25,000,000
Assets held-in-trust		290,000,000		290,000,000		280,000,000
Limited Liability Company [Member]
Schedule of Investments [Line Items]
Equity Method Investments, Fair Value Disclosure		61,000,000		61,000,000
Future Equity Investments [Member]
Schedule of Investments [Line Items]
Remaining minimum amount committed		84,000,000		84,000,000
AGL Subsidiaries [Member]
Schedule of Investments [Line Items]
Assets held-in-trust		1,422,000,000		1,422,000,000		1,502,000,000
Maximum [Member] \| Future Equity Investments [Member]
Schedule of Investments [Line Items]
Long-term purchase commitment, amount	$ 100,000,000
Assured Investment Management Funds [Member] \| Maximum [Member] \| AGL Subsidiaries [Member] \| Future Equity Investments [Member]
Schedule of Investments [Line Items]
Long-term purchase commitment, amount				500,000,000		500,000,000
Assured Investment Management Funds [Member] \| Maximum [Member] \| AGL Subsidiaries [Member] \| Equity Method Investments [Member]
Schedule of Investments [Line Items]
Long-term purchase commitment, amount				354,000,000		79,000,000
Long-term purchase commitment fair value		$ 367,000,000		367,000,000		$ 77,000,000
Various Future Consolidated Assured Investment Management Funds [Member] \| Maximum [Member] \| AGL Subsidiaries [Member] \| Future Equity Investments [Member]
Schedule of Investments [Line Items]
Long-term purchase commitment, amount				$ 112,000,000
Number of Investment Funds \| Investment_Funds		4		4
Individually Managed Accounts with BlueMountain [Member] \| Maximum [Member] \| AGL Subsidiaries [Member] \| Municipal Obligations [Member]
Schedule of Investments [Line Items]
Long-term purchase commitment, amount				$ 250,000,000
Individually Managed Accounts with BlueMountain [Member] \| Maximum [Member] \| AGL Subsidiaries [Member] \| Collateralized Loan Obligations [Member]
Schedule of Investments [Line Items]
Long-term purchase commitment, amount				100,000,000
Long-term purchase commitment, additional authorized amount				$ 200,000,000