Reinsurance (Details 4) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Calculation of net reserves, net unearned premium and net deferred policy acquisition costs
Loss and loss adjustment expense payable	$ 3,686,570	$ 3,471,858
Reinsurance recoverable on outstanding losses	(475,671)	(452,882)
Reinsurance recoverable on incurred but not reported losses	(542,049)	(481,204)
Net reserves	2,668,850	2,537,772
Unearned premium	1,071,340	1,045,877
Ceded unearned premium	(231,537)	(278,663)
Net unearned premium	839,803	767,214
Deferred policy acquisition costs	225,190	212,786
Deferred ceding commissions	(66,059)	(72,565)
Net deferred policy acquisition costs	$ 159,131	$ 140,221

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The amount of deferred ceded commissions capitalized on contracts remaining in force as of the balance sheet date.

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Net reserves.

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Net unearned premium.

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Net amount of deferred policy acquisition costs capitalized on contracts remaining in force as of the balance sheet date.

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The amount needed to reflect the estimated ultimate cost of settling claims relating to casualty insurance insured events that have occurred on or before a particular date (ordinarily, the balance sheet date) and the amount needed to provide for the estimated ultimate cost required to investigate and settle claims relating to insured events that have occurred on or before a particular date (ordinarily, the balance sheet date), whether or not reported to the insurer at that date.

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The unexpired portion of premiums ceded on policies in force as of the balance sheet date.

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The sum for all reinsurance arrangements of the known and estimated amount recoverable as of the balance sheet date from a given reinsurer for claims paid or incurred by the ceding insurer and associated claims settlement expenses for each reinsurance arrangement (or, the sum of all cases determined individually, probably applying different assumptions to each arrangement).

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The portion of reinsurance receivables representing the aggregate amount of estimated amounts due as of the balance sheet date from another insurer; also called reinsurance recoverables or unpaid losses recoverable, that are expected based upon statistical projections of incurred claims and claims settlement expenses which have not yet been reported to the insurer.

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Carrying amount of premiums written on insurance contracts that have not been earned as of the balance sheet date.

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