Commitments and Contingencies - Approximate Aggregate Minimum Future Rental Payments Required (Details) (USD $)	Dec. 31, 2012
Operating Leased Assets
2013	$ 13,510,643
2014	12,305,134
2015	11,348,919
2016	9,962,731
2017	9,926,646
Thereafter	25,850,372
Total	$ 82,904,445	[1]

[1] Minimum future rental payments are recorded at their gross amounts and have not been reduced by sublease rentals of $1.1 million for each year from 2013 to 2015 for approximately 15,000 square feet of space in our New York office, which has been sublet to GCP Capital through December 2015. Under the terms of the sublease, the lease may be terminated earlier than 2015.