Summary of Significant Accounting Policies - Additional Information (Detail) (USD $)	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011	Dec. 31, 2011	Dec. 31, 2010
Significant Accounting Policies [Line Items]
Client reimbursements	$ 2,400,000	$ 1,800,000	$ 3,800,000	$ 3,100,000
Cash on deposit with financial institutions	41,610,000	59,379,000	41,610,000	59,379,000	62,050,000	78,227,000
Carrying value of cash equivalents	5,100,000		5,100,000		2,100,000
Cash and cash equivalents, restricted from use	6,900,000		6,900,000		7,300,000
Long term receivables related to private equity and real estate capital advisory engagements	27,400,000		27,400,000		21,300,000
Installments period	3 years		3 years		3 years
Depreciation and amortization of property and equipment			Depreciation is computed using the straight-line method over the life of the assets. Amortization of leasehold improvements is computed using the straight-line method over the lesser of the life of the asset or the remaining term of the lease
Aircraft
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			7 years
Equipment
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			5 years
Furniture and Fixtures
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			7 years
Leasehold Improvements
Significant Accounting Policies [Line Items]
Estimated useful lives of fixed assets (in years)			10 years
Estimated useful lives of fixed assets, description			Lesser of 10 years or the remaining lease term
Deferred Compensation Plan
Significant Accounting Policies [Line Items]
Cash and cash equivalents, restricted from use	$ 2,500,000		$ 2,500,000		$ 2,900,000
Maximum
Significant Accounting Policies [Line Items]
Cash and equivalents, maturity date			3 months		3 months
Maximum | Restricted Stock
Significant Accounting Policies [Line Items]
Compensation expense amortization period/service period following the date of grant			5 years
Minimum | Restricted Stock
Significant Accounting Policies [Line Items]
Compensation expense amortization period/service period following the date of grant			3 years