v2.3.0.15

Fair Value Measurements (Narrative) (Details) (USD $)	9 Months Ended			3 Months Ended		9 Months Ended	3 Months Ended		9 Months Ended		3 Months Ended		9 Months Ended						48 Months Ended					3 Months Ended																	3 Months Ended		9 Months Ended
	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2010 Other Investments [Member]	Sep. 30, 2011 Other Investments [Member]	Sep. 30, 2010 Other Investments [Member]	Sep. 30, 2011 Other Investments [Member]	Sep. 30, 2011 Reinsurance Contracts Accounted For At Fair Value [Member]	Sep. 30, 2010 Reinsurance Contracts Accounted For At Fair Value [Member]	Sep. 30, 2011 Reinsurance Contracts Accounted For At Fair Value [Member]	Sep. 30, 2010 Reinsurance Contracts Accounted For At Fair Value [Member]	Sep. 30, 2011 Other Assets and Liabilities [Member]	Sep. 30, 2010 Other Assets and Liabilities [Member]	Sep. 30, 2011 Other Assets and Liabilities [Member]	Sep. 30, 2010 Other Assets and Liabilities [Member]	Sep. 30, 2011 Reinsurance Contract Liabilities Accounted For At Fair Value [Member]	Dec. 31, 2010 Reinsurance Contract Liabilities Accounted For At Fair Value [Member]	Sep. 30, 2011 Reinsurance Contract Assets Accounted For At Fair Value [Member]	Dec. 31, 2010 Reinsurance Contract Assets Accounted For At Fair Value [Member]	Dec. 31, 2014 5.875% Senior Notes Due February 15, 2013 [Member]	Feb. 15, 2013 5.875% Senior Notes Due February 15, 2013 [Member]	Sep. 30, 2011 5.875% Senior Notes Due February 15, 2013 [Member]	Dec. 31, 2010 5.875% Senior Notes Due February 15, 2013 [Member]	Jan. 03, 2003 5.875% Senior Notes Due February 15, 2013 [Member]	Mar. 31, 2010 5.75% Senior Notes Due March 15, 2020 [Member]	Sep. 30, 2011 5.75% Senior Notes Due March 15, 2020 [Member]	Dec. 31, 2010 5.75% Senior Notes Due March 15, 2020 [Member]	Sep. 30, 2011 Senior Secured Bank Loan Funds [Member]	Sep. 30, 2011 Corporate [Member]	Sep. 30, 2011 U.S. Treasuries [Member]	Sep. 30, 2011 Non-U.S. Fixed Income Funds [Member]	Sep. 30, 2011 Hedge Funds [Member]	Sep. 30, 2011 Agencies [Member]	Sep. 30, 2011 FDIC Guaranteed Corporate [Member]	Sep. 30, 2011 Non-U.S. Government Backed-Corporate [Member]	Sep. 30, 2011 Non Agency Prime Residential Mortgage Backed Securities [Member] years	Sep. 30, 2011 AltA Non Agency Mortgage Backed Securities [Member] years	Sep. 30, 2011 Agency Mortgage-Backed [Member] years	Sep. 30, 2011 Commercial Mortgage-Backed [Member] years	Sep. 30, 2011 Asset-Backed [Member] years	Sep. 30, 2011 Non-U.S. Government (Sovereign Debt) [Member]	Sep. 30, 2011 Other Secured Assets [Member]	Sep. 30, 2010 Other Secured Assets [Member]	Sep. 30, 2011 Other Secured Assets [Member]	Sep. 30, 2010 Other Secured Assets [Member]
Weighted average effective yield																												4.60%	0.90%			0.50%	0.40%	1.20%	7.40%	8.80%	1.80%	3.50%	1.00%	1.60%
Debt instrument maturity date																			February 15, 2013					March 15, 2020
Weighted average life of fixed maturity investments																																			4.0	3.8	2.8	4.1	1.2
Investments redeemable in part, on a monthly basis, or in whole over a three month period																											$ 231,300,000
Investment in closed end fund																											12,500,000
Investments, fair value															100,000		4,500,000	1,800,000
Hedge fund side pocket investments																															6,800,000
Gain (loss) on contracts							2,700,000	(800,000)	39,900,000	3,100,000
Unrealized gain (loss) on contracts											45,500,000	600,000	2,200,000	1,500,000
Senior notes interest rate																				5.875%				5.75%
Fair value of Senior Notes																					102,900,000	105,900,000			256,300,000	252,400,000
Senior Notes																							100,000,000	250,000,000
Net unrealized gains (losses) related to changes in fair value of secured assets recorded in other income (losses)																																										300,000	100,000	100,000
Investments redeemable on bi-monthly basis																														29,400,000
Net unrealized gains included in other income (loss)	$ 16,018,000	$ 21,005,000	$ 21,000,000	$ 42,900,000	$ 15,300,000	$ 9,200,000

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This item represents the weighted average life in years of the debt securities.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of reinsurance contracts accounted for at fair value, held at each balance sheet date and included in earnings for the period.

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This item represents 'side pocket' investments which are not redeemable at the option of the shareholder.

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This item represents senior secured bank loan funds in a closed end fund, which the Company has no right to redeem.

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This item represents the fair value of investments redeemable in part, on a monthly basis, or in whole over a three month period.

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This item represents the fair value of investments redeemable, in whole or in part, on a bi-monthly basis.

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Net unrealized gains related to changes in fair value of other assets and liabilities recorded in other income.

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Net Unrealized Gains Related To Changes In Fair Value Of Secured Assets Recorded In Other Income

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This item represents the weighted average effective yield percentage of debt securities.

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Interest rate stated in the contractual debt agreement.

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Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

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Value of the investment at close of period. For schedules of investments that are categorized, the value would be aggregated by category. For investment in and advances to affiliates, if operations of any controlled companies are different in character from those of the company, group such affiliates within divisions and by type of activities.

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The fair value amount of long-term debt whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

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The net change in the difference between the fair value and the carrying value, or in the comparative fair values, of investments, not including unrealized gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity, held at each balance sheet date and included in earnings for the period.

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