Segment Operating Results (Footnotes) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014		Dec. 31, 2013		Dec. 31, 2012
Segment Reporting Information [Line Items]
Other Revenue, net	$ (4,252)		$ 2,863		$ (5,655)
Special Charges	4,893		170		662
Acquisition and Transition Costs	5,828		58		840
Other Expenses	25,437	[1]	36,447	[1]	53,452	[1]
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	(1,722)	[2]	3,979	[2]	(3,019)	[2]
Interest expense on Senior Notes	4,470		4,386		4,312
Other Revenue, net, Changes in Tax Receivable Agreement			5,524
Amortization of LP Units and Certain Other Awards	3,399		17,817		18,601
Other Acquisition Related Compensation Charges	7,939		15,923		28,163
Special Charges	4,893		0		662
Intangible Asset and Other Amortization	2,494		0		3,348
Professional Fees	1,672		0		0
Acquisition and Transition Costs	4,712		0		0
Other Expenses	25,109	[1]	33,740	[1]	50,774	[1]
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	(2,530)	[3]	(1,116)	[3]	(2,636)	[3]
Interest expense on Senior Notes	3,770		3,702		3,643
Other Revenue, net, Changes in Tax Receivable Agreement			1,381
Amortization of LP Units and Certain Other Awards	0		2,209		2,350
Special Charges	0		170		0
Intangible Asset and Other Amortization	328		328		328
Other Expenses	$ 328	[1]	$ 2,707	[1]	$ 2,678	[1]

[1] Other Expenses are as follows: For the Years Ended December 31, 2014 2013 2012Investment Banking Amortization of LP Units and Certain Other Awards$3,399 $17,817 $18,601Other Acquisition Related Compensation Charges7,939 15,923 28,163Special Charges4,893 — 662Intangible Asset and Other Amortization2,494 — 3,348Professional Fees1,672 — —Acquisition and Transition Costs4,712 — —Total Investment Banking25,109 33,740 50,774Investment Management Amortization of LP Units and Certain Other Awards— 2,209 2,350Special Charges— 170 —Intangible Asset and Other Amortization328 328 328Total Investment Management328 2,707 2,678Total Other Expenses$25,437 $36,447 $53,452

[2] Investment Banking Other Revenue, net, includes interest expense on the Senior Notes of $4,470, $4,386 and $4,312 for the years ended December 31, 2014, 2013 and 2012, respectively, and changes in amounts due pursuant to the Company'stax receivable agreement of $5,524 for the year ended December 31, 2013.

[3] Investment Management Other Revenue, net, includes interest expense on the Senior Notes of $3,770, $3,702 and $3,643 for the years ended December 31, 2014, 2013 and 2012, respectively, and changes in amounts due pursuant to theCompany's tax receivable agreement of $1,381 for the year ended December 31, 2013.