Losses and Loss Adjustment Expenses (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Liability for losses and loss adjustment expenses
Balance, beginning of period	$ 41,168	$ 27,424
Incurred related to:
Current period	16,931	18,406
Prior period	(1,059)	762
Total incurred	15,872	19,168
Paid related to:
Current period	(3,732)	(4,391)
Prior period	(11,557)	(8,725)
Total paid	(15,289)	(13,116)
Balance, end of period	$ 41,751	$ 33,476