Segment Reporting - Additional Information (Details)	9 Months Ended
	Sep. 30, 2021 segment offering
Segment Reporting Information [Line Items]
Number of reportable segments | segment	5
Corporate Finance
Segment Reporting Information [Line Items]
Number of core offerings	3
FLC
Segment Reporting Information [Line Items]
Number of core offerings	5
Economic Consulting
Segment Reporting Information [Line Items]
Number of core offerings	3
Strategic Communications
Segment Reporting Information [Line Items]
Number of core offerings	3