Agreements with Related Parties (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
[AtradiusNvMember]
Related Party Transaction [Line Items]
Net premiums written	$ 80,292	$ 75,991	$ 80,975
Net premiums earned	75,714	77,230	69,094
Losses and loss expenses and life policy benefits	35,197	32,595	40,740
Acquisition costs	28,475	33,906	22,012
Reinsurance balances receivable	11,974	5,332
Unpaid losses and loss expenses	82,711	75,173
Unearned premiums	40,312	34,836
Other net assets	12,135	14,187
[DeltaLloydMember]
Related Party Transaction [Line Items]
Net premiums earned		1,900	1,200
Losses and loss expenses and life policy benefits		800	300
Unpaid losses and loss expenses		7,500
[IngGroupNvMember]
Related Party Transaction [Line Items]
Net premiums earned	3,400
Losses and loss expenses and life policy benefits	800
Unpaid losses and loss expenses	$ 12,700