Business Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2014 Segment	Dec. 31, 2013	Dec. 31, 2012
Segment Reporting Disclosure [Line Items]
Number of Reportable Segments	1
Number of principal sources of revenue (source of revenue)	2
Advisory revenues as a percentage of total revenue	102.00%	100.00%	102.00%
Advisory revenues
Segment Reporting Disclosure [Line Items]
Number of clients that accounted for more than 10% of total revenues (entities)	0	1	0
Investment Revenues
Segment Reporting Disclosure [Line Items]
Number of individual investments accounting for more than 10% of total revenues (investments)	0	0	0