Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Assets
Securities owned, at fair value:	$ 5,763	$ 5,277
Liabilities
Securities sold, not yet purchased, at fair value:	1,757	438
Recurring basis \| Total
Assets
Total Assets	143,788	124,591
Liabilities
Total Liabilities	1,768	441
Recurring basis \| Total \| Tax free money market mutual funds
Assets
Cash and cash equivalents:	4,533	2,041
Recurring basis \| Total \| U.S. government money market mutual funds
Assets
Cash and cash equivalents:	128,877	110,901
Recurring basis \| Total \| Money market mutual funds
Assets
Cash and cash equivalents:	4,615	6,372
Recurring basis \| Total \| Corporate stocks-trading securities
Assets
Securities owned, at fair value:	973	689
Liabilities
Securities sold, not yet purchased, at fair value:	1,757	438
Recurring basis \| Total \| Mutual funds
Assets
Securities owned, at fair value:	4,790	4,588
Recurring basis \| Total \| Currency forward contracts
Liabilities
Accounts payable and accrued expenses:	11	3
Recurring basis \| Level 1
Assets
Total Assets	143,788	124,591
Liabilities
Total Liabilities	1,757	438
Recurring basis \| Level 1 \| Tax free money market mutual funds
Assets
Cash and cash equivalents:	4,533	2,041
Recurring basis \| Level 1 \| U.S. government money market mutual funds
Assets
Cash and cash equivalents:	128,877	110,901
Recurring basis \| Level 1 \| Money market mutual funds
Assets
Cash and cash equivalents:	4,615	6,372
Recurring basis \| Level 1 \| Corporate stocks-trading securities
Assets
Securities owned, at fair value:	973	689
Liabilities
Securities sold, not yet purchased, at fair value:	1,757	438
Recurring basis \| Level 1 \| Mutual funds
Assets
Securities owned, at fair value:	4,790	4,588
Recurring basis \| Level 2
Liabilities
Total Liabilities	11	3
Recurring basis \| Level 2 \| Currency forward contracts
Liabilities
Accounts payable and accrued expenses:	$ 11	$ 3

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item includes currency on hand as well as demand deposits with banks or financial institutions. It also includes other kinds of accounts that have the general characteristics of demand deposits in that the Company may deposit additional funds at any time and also effectively may withdraw funds at any time without prior notice or penalty. Cash equivalents, excluding items classified as marketable securities, include short-term, highly liquid investments that are both readily convertible to known amounts of cash, and so near their maturity that they present minimal risk of changes in value because of changes in interest rates. Generally, only investments with original maturities of three months or less qualify under that definition. Original maturity means original maturity to the entity holding the investment. For example, both a three-month US Treasury bill and a three-year Treasury note purchased three months from maturity qualify as cash equivalents. However, a Treasury note purchased three years ago does not become a cash equivalent when its remaining maturity is three months.

+ References+ Details

The aggregate fair value as of the balance sheet date of financial instruments and other positions owned by the entity including: (1) mortgages, mortgage-backed and asset backed securities; (2) US government and agency obligations; (3) state and municipal government obligations; (4) other sovereign government debt; (5) corporate obligations; (6) corporate equities; (7) principal investments; (8) derivative contracts; and (9) physical commodities. Includes both pledged and unpledged holdings.

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- Definition

Carrying value as of the balance sheet date of obligations incurred from short sales.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Chapter 7

-Paragraph 40

-IssueDate 2006-05-01

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 940

-SubTopic 320

-Section 35

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6475908&loc=d3e42429-110968

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Chapter 4

-Paragraph 38

-IssueDate 2006-05-01

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Chapter 7

-Paragraph 19

-IssueDate 2006-05-01

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Audit and Accounting Guide (AAG)

-Number AAG-BRD

-Chapter 7

-Paragraph 2

-IssueDate 2006-05-01

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

+ Details