Reinsurance - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($) Reinsurers	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($) Reinsurers	Sep. 30, 2014 USD ($)	Dec. 31, 2014 USD ($) Reinsurers
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Number of reinsurers | Reinsurers	21		21		28
Reinsurance recoverable	$ 0		$ 0		$ 0
Credit risk associated with reinsurance receivables	0		0		0
Recoveries pertaining to reinsurance contracts	0	$ 0	0	$ 0
Net reduction in ceded premiums	2,901,000	$ 6,512,000	15,515,000	$ 17,052,000
Other assets	38,440,000		38,440,000		35,587,000
Prepaid reinsurance premiums	26,590,000		26,590,000		34,096,000
Reinsurance [Member]
Reinsurance Premiums for Insurance Companies, by Product Segment [Line Items]
Other assets	31,836,000		31,836,000		28,596,000
Prepaid reinsurance premiums	$ 4,158,000		$ 4,158,000		$ 5,983,000