Reinsurance - Schedule of Unsecured Reinsurance Recoverables from Reinsurers (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	$ 91,077	$ 85,888
Letters of credit and funds held	(53,572)
Total unsecured reinsurance recoverables	37,505
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk [Member] | Hannover Reinsurance (Ireland) Limited (A+) [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	35,530
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk [Member] | Odyssey America Reinsurance Corporation (A) [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	12,127
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk [Member] | Minnesota Workers' Compensation Reinsurance Association (NR) [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	9,034
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk [Member] | Tokio Millenium Reinsurance Limited (A++) [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	7,294
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk [Member] | Clearwater Insurance Company (bbb) [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	5,610
Reinsurance Recoverable [Member] | Reinsurer Concentration Risk [Member] | Other Reinsurers [Member]
Ceded Credit Risk [Line Items]
Total reinsurance recoverables	$ 21,482