Segment Operating Results (Footnotes) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Segment Reporting Information [Line Items]
Other Revenue, net	$ (5,716)	$ (4,252)	$ 2,863
Special Charges	41,144	4,893	170
Acquisition and Transition Costs	4,890	5,828	58
Other Expenses	148,071	25,437	36,447
Investment Banking [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	(2,945)	(1,722)	3,979
Interest expense on Senior Notes	6,041	4,470	4,386
Other Revenue, net, Changes in Tax Receivable Agreement			5,524
Amortization of LP Units / Interests and Certain Other Awards	83,673	3,399	17,817
Other Acquisition Related Compensation Charges	1,537	7,939	15,923
Special Charges	2,151	4,893	0
Professional Fees Other Expenses	0	1,672	0
Acquisition and Transition Costs	4,879	4,712	0
Changes To Fair Value Of Contingent Consideration	2,704	0	0
Intangible Asset and Other Amortization	13,795	2,494	0
Other Expenses	108,739	25,109	33,740
Investment Management [Member]
Segment Reporting Information [Line Items]
Other Revenue, net	(2,771)	(2,530)	(1,116)
Interest expense on Senior Notes	3,576	3,770	3,702
Other Revenue, net, Changes in Tax Receivable Agreement			1,381
Amortization of LP Units / Interests and Certain Other Awards	0	0	2,209
Special Charges	38,993	0	170
Acquisition and Transition Costs	11	0	0
Intangible Asset and Other Amortization	328	328	328
Other Expenses	$ 39,332	$ 328	$ 2,707