Goodwill and Intangible Assets - Changes in Carrying Amount of Goodwill (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Goodwill [Line Items]
Goodwill					$ 1,042,756
Accumulated impairment losses					(396,076)
Goodwill, Acquired During Period			$ 495
Goodwill, Impairment Loss	$ 0	$ 0	(59,816)	$ 0
Goodwill, Foreign Currency Translation Gain (Loss)			(629)
Goodwill, net ending balance	586,730		586,730		646,680
Healthcare
Goodwill [Line Items]
Goodwill					636,810
Accumulated impairment losses					(208,081)
Goodwill, Acquired During Period			0
Goodwill, Impairment Loss			0
Goodwill, Foreign Currency Translation Gain (Loss)			0
Goodwill, net ending balance	428,729		428,729		428,729
Education [Member]
Goodwill [Line Items]
Goodwill					103,889
Accumulated impairment losses					0
Goodwill, Acquired During Period			495
Goodwill, Impairment Loss			0
Goodwill, Foreign Currency Translation Gain (Loss)			0
Goodwill, net ending balance	104,384		104,384		103,889
Business Advisory
Goodwill [Line Items]
Goodwill					302,057
Accumulated impairment losses					(187,995)
Goodwill, Acquired During Period			0
Goodwill, Impairment Loss			59,816
Goodwill, Foreign Currency Translation Gain (Loss)			(629)
Goodwill, net ending balance	$ 53,617		$ 53,617		$ 114,062