Reasonable Representation of Each Segment's Contribution (Parenthetical) (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012		Dec. 31, 2011		Dec. 31, 2010
Segment Reporting Information [Line Items]
Total Other Revenue, net	$ (5,655)		$ (5,494)		$ (636)
Investment Banking Other Revenue, net, includes interest expense on the Senior Notes	4,312		4,238		4,169
Investment Management Other Revenue, net, includes interest expense on the Senior Notes	3,643		3,579		3,525
Special Charges	662		3,894
Total Other Expenses	53,452	[1]	61,297	[1]	23,029	[1]
Investment Banking
Segment Reporting Information [Line Items]
Total Other Revenue, net	(3,019)	[2]	(2,473)	[2]	(84)	[2]
Amortization of LP Units and Certain Other Awards	18,601		21,328		17,532
Vesting of Event-based Awards			8,906
Acquisition Related Compensation Charges	28,163		14,618
Special Charges	662		3,894
Intangible Asset Amortization	3,348		6,845		1,876
Total Investment Banking	50,774	[1]	55,591	[1]	19,408	[1]
Investment Management
Segment Reporting Information [Line Items]
Total Other Revenue, net	(2,636)	[3]	(3,021)	[3]	(552)	[3]
Amortization of LP Units and Certain Other Awards	2,350		2,892		3,289
Vesting of Event-based Awards			2,483
Intangible Asset Amortization	328		331		332
Total Investment Management	$ 2,678	[1]	$ 5,706	[1]	$ 3,621	[1]

[1] Other Expenses are as follows: For the Years Ended December 31, 2012 2011 2010 Investment Banking Amortization of LP Units and Certain Other Awards $ 18,601 $ 21,328 $ 17,532 Vesting of Event-based Awards - 8,906 - Acquisition Related Compensation Charges 28,163 14,618 - Special Charges 662 3,894 - Intangible Asset Amortization 3,348 6,845 1,876 Total Investment Banking 50,774 55,591 19,408 Investment Management Amortization of LP Units and Certain Other Awards 2,350 2,892 3,289 Vesting of Event-based Awards - 2,483 - Intangible Asset Amortization 328 331 332 Total Investment Management 2,678 5,706 3,621 Total Other Expenses $ 53,452 $ 61,297 $ 23,029

[2] Investment Banking Other Revenue, net, includes interest expense on the Senior Notes of $4,312, $4,238 and $4,169 for the years ended December 31, 2012, 2011 and 2010, respectively.

[3] Investment Management Other Revenue, net, includes interest expense on the Senior Notes of $3,643, $3,579 and $3,525 for the years ended December 31, 2012, 2011 and 2010, respectively.