Losses and Loss Adjustment Expenses - Total Losses and Loss Adjustment Expense Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Effects of Reinsurance [Line Items]
Outstanding losses	$ 3,283,862	$ 2,663,161
IBNR	2,584,612	1,996,833
Fair value adjustments	(148,325)	(150,573)
Total	5,720,149	4,509,421
Non-Life Run-Off Segment
Effects of Reinsurance [Line Items]
Outstanding losses	2,757,774	2,202,187
IBNR	1,991,009	1,406,420
Fair value adjustments	(163,329)	(173,597)
Total	4,585,454	3,435,010	$ 4,004,513	$ 3,650,127
Atrium
Effects of Reinsurance [Line Items]
Outstanding losses	68,913	73,803
IBNR	115,613	113,149
Fair value adjustments	16,491	25,659
Total	201,017	212,611	215,392	$ 0
StarStone Segment
Effects of Reinsurance [Line Items]
Outstanding losses	457,175	387,171
IBNR	477,990	477,264
Fair value adjustments	(1,487)	(2,635)
Total	$ 933,678	$ 861,800	$ 0

Liability for title claims and claims adjustment expense fair value adjustments.

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- Definition

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.

+ References

No definition available.

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- Definition

The amount needed to reflect the estimated ultimate cost of settling claims relating to insured events that have occurred on or before the balance sheet date, whether or not reported to the insurer at that date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a),(b),(c)
-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

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- Definition

Estimated costs as of the balance sheet date of settling insured claims and costs incurred in the claims settlement process for claims that have not yet been submitted to the insurance company for reimbursement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section S99
-Paragraph 1
-Subparagraph (SAB TOPIC 5.W)
-URI http://asc.fasb.org/extlink&oid=27015833&loc=d3e570705-122907

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a),(b)
-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Staff Accounting Bulletin (SAB)
-Number Topic 5
-Section W

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- Definition

Costs of settling insured claims and costs incurred in the claims settlement process for the specified year specifically for claims that have already been submitted to the insurance company for reimbursement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 40
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6482485&loc=d3e14764-158437

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