Fair value of cash and securities pledged to derivative counterparties.

No definition available.

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- Definition

Fair value of securities deposited with governmental authorities.

+ References

No definition available.

+ Details

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- Definition

Market Value of Secured Note Collateral

+ References

No definition available.

+ Details

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- Definition

Fair Value of securities held to collateralize and fund repayment of debt issued through a resecuritization transaction.

+ References

No definition available.

+ Details

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- Definition

Unsettled Amounts Secured Notes from LSNI

+ References

No definition available.

+ Details

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- Definition

Line items represent reporting 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.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Article 12
-Section 12
-Sentence Column A

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- Definition

Amount awarded from other party in judgment or settlement of litigation.

+ References

No definition available.

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- Definition

Amount of investments classified as other.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03.1(f,g))
-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Investments - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2018	Jun. 30, 2018	Dec. 31, 2017
Investment [Line Items]
Other Investments		$ 391,217		$ 431,630
Cash recoveries	$ 995,000
Securities fair value		5,975		5,974
Fair value of securities held by bankruptcy remote trust		0		346,212
Market Value of Secured Note Collateral		209,983
Real Estate [Member]
Investment [Line Items]
Other Investments		16,123		33,154
Hedge Funds, Multi-strategy [Member]
Investment [Line Items]
Other Investments		0		53,054
Interest Rate Contract [Member]
Investment [Line Items]
Other Investments		177,357		136,603
Illiquid Investments [Member]
Investment [Line Items]
Other Investments		84,297		67,787
Insurance Linked [Member]
Investment [Line Items]
Other Investments		29,318		22,666
Equity [Member]
Investment [Line Items]
Other Investments		43,954		53,675
Equity investments in pooled funds [Member]
Investment [Line Items]
Other Investments		351,049		366,939
Reported Value Measurement [Member] \| Interest Rate Contract [Member]
Investment [Line Items]
Other Investments			$ 27,154	2,823
Investment Portfolio [Member]
Investment [Line Items]
Fair Value of Cash and Securities Pledged to Derivative Counterparties		102,904		$ 120,645
Ambac Assurance [Member]
Investment [Line Items]
Unsettled Amounts Secured Notes from LSNI		$ 19,405