Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Dec. 31, 2014
Significant Accounting Policies [Line Items]
Client reimbursements	$ 1,200,000	$ 1,000,000	$ 3,200,000	$ 1,700,000
Bad debt expense	200,000	0	300,000	0
Long term receivables related to private equity and real estate capital advisory engagements	33,500,000		$ 33,500,000		$ 37,300,000
Installments period			3 years
Depreciation and amortization of property and equipment			Depreciation is computed using the straight-line method over the life of the assets. Amortization of leasehold improvements is computed using the straight-line method over the lesser of the life of the asset or the remaining term of the lease.
Aircraft
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			7 years
Equipment
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			5 years
Furniture and Fixtures
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			7 years
Leasehold Improvements
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			10 years
Description of estimated useful lives			Lesser of 10 years or the remaining lease term
Restricted Stock
Significant Accounting Policies [Line Items]
Restricted stock units, amortization service period			5 years
Capital advisory engagements
Significant Accounting Policies [Line Items]
Interest income on long term receivables	$ 200,000	$ 200,000	$ 400,000	$ 400,000