Commitments and Contingencies (Details) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
	Sep. 30, 2013 Guarantee_contracts	Dec. 31, 2012 Guarantee_contracts
Guarantor Obligations [Line Items]
Opening number of financial guarantee contracts	4	4
Number of financial guarantee contracts matured, prepaid or commuted during the period	(1)	0
Closing number of financial guarantee contracts	3	4
Principal outstanding	$ 108,255	$ 115,464
Interest outstanding	0	0
Aggregate exposure outstanding	108,255	115,464
Total gross claim liability recorded	0	1,399
Total unearned premiums and fees recorded	170	279
Financial Guarantee Insurance Contracts Outstanding Weighted Average Contract Period	26 years 3 months 18 days	25 years 4 months 24 days
Financial Guarantee Related to Securities Including Some Issued By European Financials [Member]
Guarantor Obligations [Line Items]
Closing number of financial guarantee contracts	3
Aggregate exposure outstanding	$ 108,300