Segment Operating Results (Other Revenue) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Segment Reporting Information [Line Items]
Total Other Revenue, net	$ (1,255)	$ (1,537)	$ (4,681)	$ (4,414)
Investment Banking Other Revenue, net, includes interest expense on the Senior Notes	1,082	1,059	3,227	3,171
Investment Management Other Revenue, net, includes interest expense on the Senior Notes	914	894	2,727	2,678
Investment Banking [Member]
Segment Reporting Information [Line Items]
Total Other Revenue, net	(435)	(829)	(2,407)	(2,222)
Investment Management [Member]
Segment Reporting Information [Line Items]
Total Other Revenue, net	$ (820)	$ (708)	$ (2,274)	$ (2,192)