Reinsurance (Details 4) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Calculation of net reserves, net unearned premium and net deferred policy acquisition costs
Loss and loss adjustment expense payable	$ 3,655,944	$ 3,471,858
Reinsurance recoverable on outstanding losses	(487,294)	(452,882)
Reinsurance recoverable on incurred but not reported losses	(555,705)	(481,204)
Net reserves	2,612,945	2,537,772
Unearned premium	1,110,638	1,045,877
Ceded unearned premium	(242,599)	(278,663)
Net unearned premium	868,039	767,214
Deferred policy acquisition costs	229,248	212,786
Deferred ceding commissions	(67,015)	(72,565)
Net deferred policy acquisition costs	$ 162,233	$ 140,221
Number of days outstanding on paid losses	90 days