Non-controlling interests - Income Attributable to Non-controlling Interests (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
Mar. 31, 2014	Mar. 31, 2013
Noncontrolling Interest [Line Items]
Income (loss) attributable to non-controlling interests	$ 1,016	$ 1,083
Catastrophe Fund
Noncontrolling Interest [Line Items]
Income (loss) attributable to non-controlling interests	250	579
Catastrophe Fund Manager
Noncontrolling Interest [Line Items]
Income (loss) attributable to non-controlling interests	(59)	(64)
Joint Venture - Third Point Advisors LLC share
Noncontrolling Interest [Line Items]
Income (loss) attributable to non-controlling interests	$ 825	$ 568

Amount of income (loss) from continuing operations attributable to the noncontrolling interest. Also defined as revenue less expenses and taxes from ongoing operations before extraordinary items but after deduction of those portions of income or loss from continuing operations that are allocable to noncontrolling interests.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 45

-Paragraph 19

-URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4569616-111683

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 810

-SubTopic 10

-Section 45

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=7656940&loc=SL4568447-111683

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration