Reinsurance (Details 2) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Transatlantic Reinsurance Company [Member]
Reinsurers With Net Recoverable Balances Greater Than 25 Million [Line Items]
Total recoverables	$ 145,733	$ 129,516
Total credis	15,166	18,454
Net recoverables	130,567	111,062
Hannover Rueckversicherungs Ag [Member]
Reinsurers With Net Recoverable Balances Greater Than 25 Million [Line Items]
Total recoverables	97,281	80,986
Total credis	18,587	20,165
Net recoverables	78,694	60,821
Ace Property And Casualty Insurance Company [Member]
Reinsurers With Net Recoverable Balances Greater Than 25 Million [Line Items]
Total recoverables	70,248	81,471
Total credis	4,195	698
Net recoverables	66,053	80,773
Axis Reinsurance Company [Member]
Reinsurers With Net Recoverable Balances Greater Than 25 Million [Line Items]
Total recoverables	80,956	63,481
Total credis	11,777	11,292
Net recoverables	69,179	52,189
Arch Reinsurance Company [Member]
Reinsurers With Net Recoverable Balances Greater Than 25 Million [Line Items]
Total recoverables	41,472	44,185
Total credis	2,544	3,430
Net recoverables	38,928	40,755
Swiss Reinsurance America Corporation [Member]
Reinsurers With Net Recoverable Balances Greater Than 25 Million [Line Items]
Total recoverables		33,307
Total credis		10,475
Net recoverables		22,832
Harco National Insurance Company [Member]
Reinsurers With Net Recoverable Balances Greater Than 25 Million [Line Items]
Total recoverables		31,851
Total credis		9,952
Net recoverables		$ 21,899