Summary of Significant Accounting Policies (Policy)	6 Months Ended
Jun. 30, 2014
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the United States of America. Certain financial information and accompanying note disclosure normally included in the Company’s Annual Report on Form 10-K has been condensed or omitted. The interim financial information is unaudited but reflects all adjustments (consisting of only normal recurring adjustments) which are, in the opinion of management, necessary for a fair statement of financial position of the Company as of June 30, 2014, the results of operations for the three and six months ended June 30, 2014 and 2013, and cash flows for the six month periods ended June 30, 2014 and 2013. These interim Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and the Notes to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013. There have been no significant changes in significant accounting policies during the six months ended June 30, 2014 as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.
Cash and Cash Equivalents	Statements of Cash Flows For purposes of the Consolidated Statements of Cash Flows, the Company considers investment instruments purchased with an original maturity of three months or less to be cash equivalents.
New Accounting Pronouncements	New Accounting Pronouncements On May 28, 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), requiring an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The updated standard permits the use of either the retrospective or cumulative effect transition method. Early adoption is not permitted. ASU 2014-09 becomes effective for the Company during the first quarter 2017. The Company is currently evaluating the transition method that will be elected and the effect that the updated standard will have on its consolidated financial statements and related disclosures.
Reclassifications	Reclassifications Certain prior year amounts have been reclassified to conform to current year presentation.
Equity Method Investments	The Company accounts for its interest in LSV using the equity method because of its less than 50 percent ownership. The Company’s total partnership interest in LSV was approximately 39.3 percent during the six months ended June 30, 2014. During the six months ended June 30, 2013, the Company's total partnership interest was reduced from approximately 39.8 percent to approximately 39.3 percent. The Company’s interest in the net assets of LSV is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheets and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations.
Variable Interest Entities	The Company does not have a significant equity investment in any of the VIEs and does not have an obligation to enter into any guarantee agreements with the VIEs. The Company is not the primary beneficiary of the VIEs because the expected fees and the expected return on any investment into the VIE by the Company relative to the expected returns of the VIE to the equity investor holders does not approach 50 percent of the expected losses or gains of the VIEs. Therefore, the Company is not required to consolidate any investment products that are VIEs into its financial statements. The Company’s variable interest in the VIEs, which consists of management fees and in some situations, seed capital, is not considered a significant variable interest. The risks to the Company associated with its involvement with any of the investment products that are VIEs are limited to the cash flows received from the revenue generated for asset management, administration and distribution services and any equity investments in the VIEs. Both of these items are not significant. The Company has no other financial obligation to the VIEs. Amounts relating to fees due from the VIEs included in Receivables and amounts relating to equity investments in the VIEs included in Investments Available for Sale on the Company’s Consolidated Balance Sheets are not significant to the total assets of the Company.
Fair Value of Financial Instruments	The fair value of the Company’s financial assets and liabilities is determined in accordance with the fair value hierarchy. The fair value of the Company’s Level 1 financial assets consist mainly of investments in equity and fixed-income mutual funds that are quoted daily. Level 2 financial assets consist of Government National Mortgage Association (GNMA) mortgage-backed pass-through certificates, Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes and investment grade commercial paper. The Company's Level 2 financial assets, with the exception of the GNMA securities, were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The GNMA mortgage-backed pass-through certificates were purchased for the sole purpose of satisfying specific regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SEI Private Trust Company (SPTC). As a result, the Company's Level 2 financial assets are limited to only these types of fixed income securities. The valuation of the Company's Level 2 financial assets are based upon securities pricing policies and procedures utilized by third-party pricing vendors. The pricing policies and procedures applied during the six months ended June 30, 2014 were consistent with those as described in our Annual Report on Form 10-K at December 31, 2013.
Available-for-sale Securities	These net unrealized gains are reported as a separate component of Accumulated other comprehensive income on the accompanying Consolidated Balance Sheets.
Trading Securities	The Company records all of its trading securities on the accompanying Consolidated Balance Sheets at fair value. Unrealized gains and losses from the change in fair value of these securities are recognized in Net gain (loss) from investments on the accompanying Consolidated Statements of Operations.
Securities Owned	The Company’s broker-dealer subsidiary, SIDCO, has investments in U.S. government agency and commercial paper securities with maturity dates less than one year. These investments are reflected as Securities owned on the accompanying Consolidated Balance Sheets. Due to specialized accounting practices applicable to investments by broker-dealers, the securities are reported at fair value and changes in fair value are recorded in current period earnings.

Summary of Significant Accounting Policies (Policy)

6 Months Ended

Jun. 30, 2014

The accompanying Consolidated Financial Statements have been prepared in accordance with accounting principles generally accepted in the United States of America. Certain financial information and accompanying note disclosure normally included in the Company’s Annual Report on Form 10-K has been condensed or omitted. The interim financial information is unaudited but reflects all adjustments (consisting of only normal recurring adjustments) which are, in the opinion of management, necessary for a fair statement of financial position of the Company as of June 30, 2014, the results of operations for the three and six months ended June 30, 2014 and 2013, and cash flows for the six month periods ended June 30, 2014 and 2013. These interim Consolidated Financial Statements should be read in conjunction with the audited Consolidated Financial Statements and the Notes to the Consolidated Financial Statements included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.

There have been no significant changes in significant accounting policies during the six months ended June 30, 2014 as compared to the significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2013.

Cash and Cash Equivalents

Statements of Cash Flows

For purposes of the Consolidated Statements of Cash Flows, the Company considers investment instruments purchased with an original maturity of three months or less to be cash equivalents.

New Accounting Pronouncements

On May 28, 2014, the FASB issued Accounting Standards Update No. 2014-09, Revenue from Contracts with Customers (ASU 2014-09), requiring an entity to recognize the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers. ASU 2014-09 also requires additional disclosure about the nature, amount, timing and uncertainty of revenue and cash flows arising from customer contracts, including significant judgments and changes in judgments and assets recognized from costs incurred to obtain or fulfill a contract. The updated standard permits the use of either the retrospective or cumulative effect transition method. Early adoption is not permitted. ASU 2014-09 becomes effective for the Company during the first quarter 2017. The Company is currently evaluating the transition method that will be elected and the effect that the updated standard will have on its consolidated financial statements and related disclosures.

Reclassifications

Certain prior year amounts have been reclassified to conform to current year presentation.

Equity Method Investments

The Company accounts for its interest in LSV using the equity method because of its less than 50 percent ownership. The Company’s total partnership interest in LSV was approximately 39.3 percent during the six months ended June 30, 2014. During the six months ended June 30, 2013, the Company's total partnership interest was reduced from approximately 39.8 percent to approximately 39.3 percent. The Company’s interest in the net assets of LSV is reflected in Investment in unconsolidated affiliates on the accompanying Consolidated Balance Sheets and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliates on the accompanying Consolidated Statements of Operations.

Variable Interest Entities

The Company does not have a significant equity investment in any of the VIEs and does not have an obligation to enter into any guarantee agreements with the VIEs. The Company is not the primary beneficiary of the VIEs because the expected fees and the expected return on any investment into the VIE by the Company relative to the expected returns of the VIE to the equity investor holders does not approach 50 percent of the expected losses or gains of the VIEs. Therefore, the Company is not required to consolidate any investment products that are VIEs into its financial statements. The Company’s variable interest in the VIEs, which consists of management fees and in some situations, seed capital, is not considered a significant variable interest.

The risks to the Company associated with its involvement with any of the investment products that are VIEs are limited to the cash flows received from the revenue generated for asset management, administration and distribution services and any equity investments in the VIEs. Both of these items are not significant. The Company has no other financial obligation to the VIEs.

Amounts relating to fees due from the VIEs included in Receivables and amounts relating to equity investments in the VIEs included in Investments Available for Sale on the Company’s Consolidated Balance Sheets are not significant to the total assets of the Company.

Fair Value of Financial Instruments

The fair value of the Company’s financial assets and liabilities is determined in accordance with the fair value hierarchy. The fair value of the Company’s Level 1 financial assets consist mainly of investments in equity and fixed-income mutual funds that are quoted daily. Level 2 financial assets consist of Government National Mortgage Association (GNMA) mortgage-backed pass-through certificates, Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes and investment grade commercial paper. The Company's Level 2 financial assets, with the exception of the GNMA securities, were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The GNMA mortgage-backed pass-through certificates were purchased for the sole purpose of satisfying specific regulatory requirements imposed on our wholly-owned limited purpose federal thrift subsidiary, SEI Private Trust Company (SPTC). As a result, the Company's Level 2 financial assets are limited to only these types of fixed income securities. The valuation of the Company's Level 2 financial assets are based upon securities pricing policies and procedures utilized by third-party pricing vendors. The pricing policies and procedures applied during the six months ended June 30, 2014 were consistent with those as described in our Annual Report on Form 10-K at December 31, 2013.

Available-for-sale Securities

These net unrealized gains are reported as a separate component of Accumulated other comprehensive income on the accompanying Consolidated Balance Sheets.

Trading Securities

The Company records all of its trading securities on the accompanying Consolidated Balance Sheets at fair value. Unrealized gains and losses from the change in fair value of these securities are recognized in Net gain (loss) from investments on the accompanying Consolidated Statements of Operations.

Securities Owned

The Company’s broker-dealer subsidiary, SIDCO, has investments in U.S. government agency and commercial paper securities with maturity dates less than one year. These investments are reflected as Securities owned on the accompanying Consolidated Balance Sheets. Due to specialized accounting practices applicable to investments by broker-dealers, the securities are reported at fair value and changes in fair value are recorded in current period earnings.