Loans Payable - Summary of Covenants Relating to Three Credit Facilities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2014	Dec. 31, 2013
Line of Credit Facility [Line Items]
Total long-term bank debt	$ 483,795	$ 448,795
Accrued interest	1,444	3,651
Total loans payable	485,239	452,446
EGL Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Clarendon Facility	Jul. 08, 2013
Facility Term	5 years
Total long-term bank debt	328,800	258,800
SeaBright Facility [Member]
Line of Credit Facility [Line Items]
Clarendon Facility	Dec. 21, 2012
Facility Term	3 years
Total long-term bank debt	89,000	111,000
Clarendon Facility [Member]
Line of Credit Facility [Line Items]
Clarendon Facility	Jul. 12, 2011
Facility Term	4 years
Total long-term bank debt	$ 65,995	$ 78,995