Capital Lease, Term

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- Definition

Capital Lease, Term, Renewal Option

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No definition available.

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- Definition

Commitments and Contingencies [Line Items]

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- Definition

Private Equity Partnerships and Other Entities, Commitments Fulfilled

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- Definition

Private Equity Partnerships and Other Entities, Initial Commitments

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- Definition

Private Equity Partnerships and Other Entities, Unfunded Commitments

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
-SubTopic 10
-Section 50
-Paragraph 18
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-Publisher FASB
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 275
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-Section 50
-Paragraph 20
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-Publisher FASB
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-Section 50
-Paragraph 21
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-URI http://asc.fasb.org/extlink&oid=73719730&loc=d3e13537-108611

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- Definition

Amount of gain recognized in the period that had been disclosed in prior periods as a contingent gain.

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Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 30
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6397426&loc=d3e17499-108355

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- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

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- Definition

Reflects the estimated amount of loss from the specified contingency as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 450
-SubTopic 20
-Section 50
-Paragraph 9
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349

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- Definition

The carrying amount, as of the date of the latest financial statement presented, of all assets that are pledged as collateral for the payment of the related debt obligation primarily arising from secured borrowings, repurchase agreements or other current or potential obligations, where the secured party does not have the right by contract or custom to sell or re-pledge the collateral and therefore are not reclassified and separately reported in the statement of financial position.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 30
-Section 50
-Paragraph 1A
-Subparagraph (b)(1)(i)
-URI http://asc.fasb.org/extlink&oid=64858031&loc=SL6224234-111729

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Commitments, Contingencies and Other Items (Narrative) (Details) £ in Thousands, $ in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2016 GBP (£)	Dec. 31, 2015 USD ($)
Commitments and Contingencies [Line Items]
Initial commitments	$ 794.2
Fulfilled commitments	554.7
Unfunded commitments	$ 249.4
Initial capital lease term	20 years
Bargain renewal option term	30 years
Reduction in Taxes \| Property
Commitments and Contingencies [Line Items]
Recovery of previously recognized acquisition expenses			$ 7.7
Letter of Credit
Commitments and Contingencies [Line Items]
Letters of credit outstanding	$ 894.2
Letter of Credit \| Top Layer Reinsurance Ltd.
Commitments and Contingencies [Line Items]
Collateral pledged to support letter of credit	37.5
Maximum \| Letter of Credit \| Capital Support Agreement \| Top Layer Reinsurance Ltd.
Commitments and Contingencies [Line Items]
Maximum mandatory capital contribution in the event of loss that reduced capital and surplus below specified level	$ 50.0
Maximum \| Investments as a Percentage of Shareholders' Equity
Commitments and Contingencies [Line Items]
Concentration risk percentage	10.00%
Specialty Risks FAL Facility \| Letter of Credit \| Syndicate 1458 \| Citibank Europe PLC
Commitments and Contingencies [Line Items]
Letters of credit outstanding \| £		£ 10,000