Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019	Jan. 01, 2020	Jan. 01, 2019
Significant Accounting Policies [Line Items]
Contract with customer, liability	$ 5,800		$ 5,800		$ 3,900
Revenues	47,786	$ 56,084	114,885	$ 107,279
Accounts receivable, credit loss expense (reversal)	(800)	100	(100)	$ 400
Retained earnings	43,881		$ 43,881		69,093
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.
Operating lease right-of-use asset	83,282		$ 83,282		28,346
Operating lease obligations	87,079		$ 87,079		$ 30,750
Accounting Standards Update [Extensible List]			us-gaap:AccountingStandardsUpdate201613Member	us-gaap:AccountingStandardsUpdate201602Member	us-gaap:AccountingStandardsUpdate201613Member
Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Significant Accounting Policies [Line Items]
Operating lease right-of-use asset							$ 38,100
Operating lease obligations							38,100
Deferred rent							$ 3,200
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
Equipment
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets			5 years
Furniture and Fixtures
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets			7 years
Leasehold Improvements
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets			10 years
Restricted Stock | Minimum
Significant Accounting Policies [Line Items]
Restricted stock units, amortization service period			3 years
Restricted Stock | Maximum
Significant Accounting Policies [Line Items]
Restricted stock units, amortization service period			5 years
Capital advisory engagements
Significant Accounting Policies [Line Items]
Contract with customer, liability, revenue recognized			$ 1,900	$ 3,200
Cumulative effect of the change in accounting principle related to credit losses
Significant Accounting Policies [Line Items]
Retained earnings						$ (100)
Primary Capital Advisory Engagements
Significant Accounting Policies [Line Items]
Long term receivables related to private equity and real estate capital advisory engagements	6,900		$ 6,900		$ 10,500
Installments period			3 years
Reimbursement Revenue
Significant Accounting Policies [Line Items]
Revenues	$ 700	$ 1,400	$ 1,900	$ 2,500