Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Significant Accounting Policies [Line Items]
Client reimbursements	$ 1.9	$ 2.0
Bad debt expense	0.2	0.2
Long term receivables related to private equity and real estate capital advisory engagements	$ 30.3		$ 32.4
Installments period (in years)	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 (years)	5 years
Capital advisory engagements
Significant Accounting Policies [Line Items]
Interest income	$ 0.2	$ 0.2