Schedule III. Supplementary Insurance Information (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	$ 110,059	$ 81,684	$ 52,622
Future Policy Benefits, Losses, Claims and Loss Expenses	1,412,510	1,563,730	1,879,377
Unearned Premiums	512,386	477,888	399,517
Premium Revenue	1,062,416	1,114,626	1,069,355
Net Investment Income	124,316	208,028	165,725
Benefits, Claims, Losses and Settlement Expenses	197,947	171,287	325,211
Amortization of Deferred Policy Acquisition Costs	144,476	125,501	113,542
Other Operating Expenses	190,639	191,105	179,151
Net Written Premiums	1,068,236	1,203,947	1,102,657
Catastrophe Reinsurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	28,057	37,889	28,306
Future Policy Benefits, Losses, Claims and Loss Expenses	542,667	780,987	1,184,258
Unearned Premiums	222,864	279,465	261,456
Premium Revenue	590,845	723,705	781,738
Net Investment Income	0	0	0
Benefits, Claims, Losses and Settlement Expenses	1,757	7,908	165,209
Amortization of Deferred Policy Acquisition Costs	43,161	49,161	66,665
Other Operating Expenses	95,851	108,130	103,811
Net Written Premiums	541,608	753,078	766,035
Specialty Reinsurance
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	58,758	26,727	15,010
Future Policy Benefits, Losses, Claims and Loss Expenses	543,710	506,268	478,313
Unearned Premiums	184,054	115,278	84,058
Premium Revenue	253,537	214,306	164,685
Net Investment Income	0	0	0
Benefits, Claims, Losses and Settlement Expenses	88,502	67,236	76,813
Amortization of Deferred Policy Acquisition Costs	60,936	41,538	23,826
Other Operating Expenses	43,370	31,780	29,124
Net Written Premiums	295,855	248,562	201,552
Lloyd's
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	23,244	17,068	9,306
Future Policy Benefits, Losses, Claims and Loss Expenses	284,447	218,367	149,470
Unearned Premiums	105,468	83,145	54,003
Premium Revenue	217,666	176,029	122,968
Net Investment Income	0	0	0
Benefits, Claims, Losses and Settlement Expenses	113,825	95,693	80,242
Amortization of Deferred Policy Acquisition Costs	46,927	34,823	22,864
Other Operating Expenses	51,115	50,540	45,680
Net Written Premiums	230,429	201,697	135,131
Other
Supplementary Insurance Information, by Segment [Line Items]
Deferred Policy Acquisition Costs	0	0	0
Future Policy Benefits, Losses, Claims and Loss Expenses	41,686	58,108	67,336
Unearned Premiums	0	0	0
Premium Revenue	368	586	(36)
Net Investment Income	124,316	208,028	165,725
Benefits, Claims, Losses and Settlement Expenses	(6,137)	450	2,947
Amortization of Deferred Policy Acquisition Costs	(6,548)	(21)	187
Other Operating Expenses	303	655	536
Net Written Premiums	$ 344	$ 610	$ (61)

Amount of amortization of deferred policy acquisition costs recognized.

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 16

-Article 12

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 235

-Section S99

-Paragraph 1

-Subparagraph (SX 210.12-16)

-URI http://asc.fasb.org/extlink&oid=34713774&loc=d3e574960-122915

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