Changes in Carrying Amounts of Goodwill by Operating Segment (Detail) (USD $) In Thousands, unless otherwise specified	6 Months Ended
	Jun. 30, 2013
Goodwill [Line Items]
Balances at December 31, 2012	$ 1,260,035
Acquisitions	20,588	[1]
Foreign currency translation adjustment	(17,457)
Balances at June 30, 2013	1,263,166
Corporate Finance / Restructuring
Goodwill [Line Items]
Balances at December 31, 2012	469,050
Acquisitions	12,393	[1]
Foreign currency translation adjustment	(4,833)
Intersegment transfers in/(out)	(31,471)	[2]
Balances at June 30, 2013	445,139
Forensic and Litigation Consulting
Goodwill [Line Items]
Balances at December 31, 2012	198,957
Acquisitions	1,050	[1]
Foreign currency translation adjustment	(2,059)
Intersegment transfers in/(out)	31,471	[2]
Balances at June 30, 2013	229,419
Economic Consulting
Goodwill [Line Items]
Balances at December 31, 2012	247,718
Acquisitions	1,925	[1]
Foreign currency translation adjustment	(506)
Balances at June 30, 2013	249,137
Technology
Goodwill [Line Items]
Balances at December 31, 2012	118,035
Foreign currency translation adjustment	(105)
Balances at June 30, 2013	117,930
Strategic Communications
Goodwill [Line Items]
Balances at December 31, 2012	226,275
Acquisitions	5,220	[1]
Foreign currency translation adjustment	(9,954)
Balances at June 30, 2013	$ 221,541

[1] Includes adjustments during the purchase price allocation period.

[2] Includes the reclassification of the Corporate Finance/Restructuring segment's healthcare practices into the Forensic and Litigation Consulting segment. See Note 15 "Segment Reporting" for information on this segment reclassification.