Concentration of Operations (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Net Premiums earned for different lines of business
Premiums earned	$ 78,741	$ 72,425	$ 69,733	$ 69,790	$ 66,211	$ 64,454	$ 60,261	$ 60,089	$ 290,689	$ 251,015	$ 218,881
Premium earned percentage									100.00%	100.00%	100.00%
Workers compensation [Member]
Net Premiums earned for different lines of business
Premiums earned									290,538	249,966	217,810
Premium earned percentage									99.90%	99.60%	99.50%
General Liability [Member]
Net Premiums earned for different lines of business
Premiums earned									$ 151	$ 1,049	$ 1,071
Premium earned percentage									0.10%	0.40%	0.50%