Investments (Schedule Of Investments In Other Ventures, Under Equity Method) (Details) (USD $)
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0 Months Ended | 1 Months Ended | |||||||||||||||||
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Dec. 31, 2011
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Dec. 31, 2010
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Dec. 31, 2011
Tower Hill Companies [Member]
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Dec. 31, 2010
Tower Hill Companies [Member]
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Jul. 01, 2008
THIG [Member]
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Dec. 31, 2011
THIG [Member]
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Dec. 31, 2010
THIG [Member]
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Dec. 31, 2011
Tower Hill [Member]
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Dec. 31, 2010
Tower Hill [Member]
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Jan. 07, 2005
Tower Hill [Member]
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Dec. 31, 2011
Tower Hill Signature [Member]
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Dec. 31, 2010
Tower Hill Signature [Member]
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Dec. 31, 2011
Top Layer Re [Member]
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Mar. 31, 2011
Top Layer Re [Member]
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Dec. 31, 2010
Top Layer Re [Member]
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Feb. 28, 2011
Top Layer Re [Member]
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Nov. 30, 2010
Top Layer Re [Member]
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Dec. 31, 2011
Other [Member]
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Dec. 31, 2010
Other [Member]
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Schedule of Equity Method Investments [Line Items] | |||||||||||||||||||
Investment | $ 131,875,000 | $ 105,875,000 | $ 60,500,000 | $ 60,000,000 | $ 50,000,000 | $ 50,000,000 | $ 50,000,000 | $ 10,000,000 | $ 10,000,000 | $ 500,000 | $ 0 | $ 65,375,000 | $ 26,875,000 | $ 13,100,000 | $ 6,000,000 | $ 19,000,000 | |||
Ownership % | 25.00% | 25.00% | 25.00% | 28.60% | 28.60% | 28.60% | 25.00% | 0.00% | 50.00% | 50.00% | 50.00% | 50.00% | 40.00% | ||||||
Equity Method Investment, Additional Contribution | 18,000,000 | 20,500,000 | 13,800,000 | ||||||||||||||||
Intangible Assets, Net (Excluding Goodwill) | 40,000,000 | ||||||||||||||||||
Goodwill | 7,800,000 | ||||||||||||||||||
Carrying Value | $ 70,714,000 | $ 85,603,000 | $ 46,818,000 | $ 52,586,000 | $ 32,645,000 | $ 38,431,000 | $ 14,173,000 | $ 14,155,000 | $ 0 | $ 0 | $ 15,872,000 | $ 14,844,000 | $ 8,024,000 | $ 18,173,000 |