Summary of Significant Accounting Policies - Additional Information (Details) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018 USD ($)	Sep. 30, 2017 USD ($)	Sep. 30, 2018 USD ($) Segment	Sep. 30, 2017 USD ($)	Jan. 01, 2018 USD ($)	Dec. 31, 2017 USD ($)
Significant Accounting Policies [Line Items]
Contract with customer, liability	$ 8,800		$ 8,800		$ 12,300
Advisory revenues	86,495	$ 48,080	261,315	$ 171,818
Provision for doubtful accounts	0	300	$ 300	1,100
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.
Retained earnings	(53,620)		$ (53,620)			$ (37,595)
Number of business segments | Segment			1
Minimum
Significant Accounting Policies [Line Items]
Amortization period of deferred cash retention awards			3 years
Maximum
Significant Accounting Policies [Line Items]
Amortization period of deferred cash retention awards			5 years
Revenue | Maximum
Significant Accounting Policies [Line Items]
Percent of revenues			1.00%
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
Estimated useful lives of fixed assets, maximum (in years)			Lesser of 10 years or the remaining lease term
Restricted Stock | Minimum
Significant Accounting Policies [Line Items]
Restricted stock units, amortization service period (years)			4 years
Restricted Stock | Maximum
Significant Accounting Policies [Line Items]
Restricted stock units, amortization service period (years)			5 years
Capital advisory engagements
Significant Accounting Policies [Line Items]
Contract with customer, liability, revenue recognized			$ 9,000
Interest income	200	200	600	500
ASC 606 Adjustments | Accounting Standards Update 2014-09
Significant Accounting Policies [Line Items]
Contract with customer, liability					(10,200)
Retained earnings					$ 7,600
Primary Capital Advisory Engagements
Significant Accounting Policies [Line Items]
Long term receivables related to private equity and real estate capital advisory engagements	24,600		$ 24,600			$ 29,300
Installments period (in years)			3 years
Reimbursement Revenue [Member]
Significant Accounting Policies [Line Items]
Advisory revenues	$ 2,100	$ 1,000	$ 5,400	$ 3,000