Reinsurance Ceded - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2014 Entity	Mar. 31, 2013
Effects of Reinsurance [Line Items]
Ceded premiums earned	$ 113.6	$ 110.9
Ceded losses incurred	$ 53.9	$ 53.6
Percentage of reinsurance recoverable of 20 largest reinsurers	76.20%
Number of largest reinsurers	20