Variable Interest Entity (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Jul. 02, 2012	Dec. 31, 2011	Sep. 30, 2011	Dec. 31, 2010
Assets and Liabilities of the VIE as consolidated in the Consolidated Balance Sheets
Cash and cash equivalents	$ 31,889	$ 3,036	$ 43,481	$ 38,199	$ 38,307
Accrued investment income	6,239		6,598
Premiums receivable	40,397	2,698	33,458
Ceded unearned premiums	28,459		22,710
Reinsurance recoverable	160,949		173,982
Deferred policy acquisition costs	26,619	1,186	24,421
Deferred income taxes	7,117	(3,060)
Other assets	92,222	9,784	74,479
Total Assets	1,368,588	31,911	1,286,532	1,277,399
Unpaid losses and loss adjustment expenses	683,011	(2,135)	680,201
Unearned premiums	148,993	(2,358)	135,059
Ceded premiums payable	16,808	(1,797)	11,425
Funds held	81,199	(3,504)	71,955
Total liabilities	1,012,779	(13,911)	951,852
VIE [Member]
Assets and Liabilities of the VIE as consolidated in the Consolidated Balance Sheets
Investments	12,132		8,346
Cash and cash equivalents	1,342		2,268
Accrued investment income	44		45
Premiums receivable	862		629
Ceded unearned premiums	424		166
Reinsurance recoverable	194		3,055
Deferred policy acquisition costs	1,317		(454)
Deferred income taxes	(21)		0
Other assets	1,537		1,042
Total Assets	17,873		15,097
Unpaid losses and loss adjustment expenses	4,907		7,412
Unearned premiums	5,192		623
Ceded premiums payable	1,100		296
Funds held	114		174
Total liabilities	$ 11,313		$ 8,505