Special Charges By Segment (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Special Charges [Line Items]
Segment special charges	$ 26,830	$ 1,750	$ 26,830	$ 6,811
Special charges	30,074	1,750	30,074	6,811
Operating Segments
Special Charges [Line Items]
Segment special charges	26,830	1,750	26,830	6,811
Operating Segments | Corporate Finance & Restructuring
Special Charges [Line Items]
Segment special charges	3,049		3,049
Operating Segments | Forensic and Litigation Consulting
Special Charges [Line Items]
Segment special charges	10,445	$ 1,750	10,445	1,750
Operating Segments | Economic Consulting
Special Charges [Line Items]
Segment special charges	5,910		5,910
Operating Segments | Technology
Special Charges [Line Items]
Segment special charges	3,827		3,827	$ 5,061
Operating Segments | Strategic Communications
Special Charges [Line Items]
Segment special charges	3,599		3,599
Unallocated Corporate
Special Charges [Line Items]
Special charges	$ 3,244		$ 3,244