Changes in Carrying Amounts of Goodwill by Operating Segment (Detail) - USD ($) $ in Thousands	3 Months Ended
Mar. 31, 2016	Dec. 31, 2015
Goodwill [Line Items]
Goodwill, Gross	$ 1,392,209	$ 1,392,437
Accumulated goodwill impairment	(194,139)	(194,139)
Goodwill, net	1,198,070	1,198,298
Foreign currency translation adjustment and other	(228)
Corporate Finance / Restructuring
Goodwill [Line Items]
Goodwill, Gross	443,188	441,548
Goodwill, net	443,188	441,548
Foreign currency translation adjustment and other	1,640
Forensic and Litigation Consulting
Goodwill [Line Items]
Goodwill, Gross	234,796	235,211
Goodwill, net	234,796	235,211
Foreign currency translation adjustment and other	(415)
Economic Consulting
Goodwill [Line Items]
Goodwill, Gross	269,239	269,341
Goodwill, net	269,239	269,341
Foreign currency translation adjustment and other	(102)
Technology
Goodwill [Line Items]
Goodwill, Gross	117,840	117,888
Goodwill, net	117,840	117,888
Foreign currency translation adjustment and other	(48)
Strategic Communications
Goodwill [Line Items]
Goodwill, Gross	327,146	328,449
Accumulated goodwill impairment	(194,139)	(194,139)
Goodwill, net	133,007	$ 134,310
Foreign currency translation adjustment and other	$ (1,303)

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 45
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6388280&loc=d3e13770-109266

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Amount before accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (a,h)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (f)
-URI http://asc.fasb.org/extlink&oid=35741047&loc=d3e13816-109267

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