Other Assets - Summary of Other Assets (Detail) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Deferred Costs Capitalized Prepaid And Other Assets Disclosure [Abstract]
Benefits receivable related to retrospective reinsurance contracts	$ 12,803	$ 8,815
Deferred costs related to retrospective reinsurance contracts	278	194
Deferred offering costs on senior notes issued in 2013	4,143	4,305
Prepaid expenses	991	771
Other	886	1,729
Total other assets	$ 19,101	$ 15,814