Variable Interest Entity (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009
Assets and Liabilities of the VIE as consolidated in the Consolidated Balance Sheets
Cash and cash equivalents	$ 20,224	$ 43,481	$ 38,307	$ 34,756
Accrued investment income	6,387	6,598
Premiums receivable	32,559	33,458
Ceded unearned premium	29,821	22,710
Reinsurance recoverable	183,562	173,982	196,590	196,080
Deferred acquisition costs	26,182	24,421
Funds on deposit	42,088	32,979
Other assets	25,849	7,532
Total assets	1,373,131	1,286,532	1,221,255
Unpaid losses and loss adjustment expenses	725,244	680,201
Unearned premiums	146,096	135,059
Ceded premiums payable	13,386	11,425
Funds held	76,806	71,955
Deferred income taxes	8,767	15,288
Total liabilities	1,028,083	951,852
VIE [Member]
Assets and Liabilities of the VIE as consolidated in the Consolidated Balance Sheets
Investments	12,144	8,346
Cash and cash equivalents	507	2,268
Accrued investment income	52	45
Premiums receivable	498	629
Ceded unearned premium	351	166
Reinsurance recoverable	5,039	3,055
Deferred acquisition costs	1,100	(454)
Funds on deposit	231	208
Other assets	1,255	834
Total assets	21,177	15,097
Unpaid losses and loss adjustment expenses	8,900	7,412
Unearned premiums	4,325	623
Ceded premiums payable	67	296
Funds held	113	174
Deferred income taxes	30	0
Total liabilities	$ 13,435	$ 8,505