Restructuring Charges - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Restructuring Charges [Abstract]
Pretax restructuring expense	$ 303	$ 600	$ 1,600	$ 233			$ 2,490	$ 1,396
Restructuring charge liability	$ 1,000						$ 1,000		$ 1,200
London Office [Member]
Restructuring Charges [Abstract]
Pretax restructuring expense				$ 200
Chicago, New York, and London Offices
Restructuring Charges [Abstract]
Pretax restructuring expense					$ 1,000
Lease payments, net of estimated sublease income charges					600
Restructuring reserve related to accelerated depreciation					$ 400
Huron Legal
Restructuring Charges [Abstract]
Pretax restructuring expense						$ 100
Severance expense			1,000
All Other
Restructuring Charges [Abstract]
Severance expense			500
Corporate Office
Restructuring Charges [Abstract]
Severance expense			$ 100