Selected Quarterly Financial Data (Unaudited) - Additional Information (Detail) (USD $)	3 Months Ended								12 Months Ended
	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Quarterly Financial Information Disclosure [Abstract]
Income before Income Taxes	$ 3,076,000	$ 2,377,000	$ 3,723,000	$ 547,000	$ 3,363,000	$ 2,096,000	$ 2,254,000	$ 2,117,000	$ 9,723,000	$ 9,830,000	$ (9,045,000)
Prior period losses and LAE paid in current period	2,600,000				2,600,000				50,590,000	49,132,000	49,315,000
Net income	21,968,000	2,120,000	3,469,000	511,000	3,158,000	1,932,000	2,066,000	2,024,000	28,068,000	9,180,000	(9,040,000)
Benefit for income taxes from change in deferred tax valuation allowance	$ 20,200,000