Related Parties - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Related Party Transaction [Line Items]
Sublease agreement	Company agreed to sublease office space to GCP Capital for a period of three to five years beginning in April 2011.
Merchant Banking Funds
Related Party Transaction [Line Items]
Due to affiliates	$ 0	$ 3,129
Sublease
Related Party Transaction [Line Items]
Recognized expense related to sublease	1,700,000	1,500,000	100,000
Payment for use of aircraft owned by executive	$ 67,840	$ 24,745	$ 10,312
Sublease | Minimum
Related Party Transaction [Line Items]
Office space lease period	3 years
Sublease | Maximum
Related Party Transaction [Line Items]
Office space lease period	5 years