Segment Reporting - Schedule of Assets by Segments (Detail) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total assets	$ 2,379,121	$ 2,257,241
Operating Segments
Segment Reporting Information [Line Items]
Total assets	2,019,863	2,040,034
Operating Segments | Corporate Finance & Restructuring
Segment Reporting Information [Line Items]
Total assets	707,924	726,176
Operating Segments | Forensic and Litigation Consulting
Segment Reporting Information [Line Items]
Total assets	412,667	401,905
Operating Segments | Economic Consulting
Segment Reporting Information [Line Items]
Total assets	516,123	501,471
Operating Segments | Technology
Segment Reporting Information [Line Items]
Total assets	171,002	195,399
Operating Segments | Strategic Communications
Segment Reporting Information [Line Items]
Total assets	212,147	215,083
Unallocated corporate assets
Segment Reporting Information [Line Items]
Total assets	$ 359,258	$ 217,207