Segment Reporting - Schedule of Assets by Segments (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Segment Reporting Information [Line Items]
Total assets	$ 2,257,241	$ 2,225,368
Operating Segments
Segment Reporting Information [Line Items]
Total assets	2,040,034	1,982,587
Operating Segments | Corporate Finance & Restructuring
Segment Reporting Information [Line Items]
Total assets	726,176	681,919
Operating Segments | Forensic and Litigation Consulting
Segment Reporting Information [Line Items]
Total assets	401,905	400,047
Operating Segments | Economic Consulting
Segment Reporting Information [Line Items]
Total assets	501,471	496,757
Operating Segments | Technology
Segment Reporting Information [Line Items]
Total assets	195,399	189,704
Operating Segments | Strategic Communications
Segment Reporting Information [Line Items]
Total assets	215,083	214,160
Unallocated Corporate assets
Segment Reporting Information [Line Items]
Total assets	$ 217,207	$ 242,781