Special Charges - Schedule Of Special Charges By Segment (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Special charges	$ 7,103,000	$ 0	$ 7,103,000	$ 0
Operating Segments
Restructuring Cost and Reserve [Line Items]
Special charges	6,730,000		6,730,000
Unallocated Corporate
Restructuring Cost and Reserve [Line Items]
Special charges	373,000		373,000
Corporate Finance & Restructuring | Operating Segments
Restructuring Cost and Reserve [Line Items]
Special charges	861,000		861,000
FLC | Operating Segments
Restructuring Cost and Reserve [Line Items]
Special charges	3,484,000		3,484,000
Economic Consulting | Operating Segments
Restructuring Cost and Reserve [Line Items]
Special charges	35,000		35,000
Technology | Operating Segments
Restructuring Cost and Reserve [Line Items]
Special charges	276,000		276,000
Strategic Communications | Operating Segments
Restructuring Cost and Reserve [Line Items]
Special charges	$ 2,074,000		$ 2,074,000