Segment Operating Results (Other Expenses) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Segment Reporting Information [Line Items]
Acquisition and Transition Costs	$ 3,465		$ 3,399		$ 712
Total Other Expenses	61,297	[1]	23,029	[1]	32,337	[1]
Investment Banking [Member]
Segment Reporting Information [Line Items]
Amortization of LP Units and Certain Other Awards	21,328		17,532		7,910
Vesting of Event-based Awards	8,906
Acquisition Related Compensation Charges	14,618
Special Charges	3,894				7,942
Intangible Asset Amortization	6,845		1,876		1,876
Total Other Expenses	55,591	[1]	19,408	[1]	17,728	[1]
Investment Management [Member]
Segment Reporting Information [Line Items]
Amortization of LP Units and Certain Other Awards	2,892		3,289		1,490
Vesting of Event-based Awards	2,483
Special Charges					12,187
Intangible Asset Amortization	331		332		220
Acquisition and Transition Costs					712
Total Other Expenses	$ 5,706	[1]	$ 3,621	[1]	$ 14,609	[1]

[1] Other Expenses are as follows: