Summary of Significant Accounting Policies (Policy)	9 Months Ended
Sep. 30, 2018
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 have 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 September 30, 2018, the results of operations for the three and nine months ended September 30, 2018 and 2017, and cash flows for the nine-month periods ended September 30, 2018 and 2017. 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, 2017. The Company adopted the requirements of Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (Accounting Standards Codification (ASC) 606 (ASC 606)) using the modified retrospective method during the nine months ended September 30, 2018. As a result of the adoption of ASC 606, the Company recorded a cumulative effect adjustment of $14,402 to retained earnings as of January 1, 2018. Prior period information has not been restated (see following caption "Revenue Recognition"). The Company also adopted ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (see Note 6) and ASU No. 2016-18, Statement of Cash Flows, Restricted Cash (Topic 230) (see following caption "Statements of Cash Flows"). All amounts and disclosures set forth in this Form 10-Q have been updated to comply with the new standards.
Revenue Recognition	Revenue Recognition Revenue is recognized when the transfer of control of promised goods or services under the terms of a contract with customers are satisfied in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those promised goods or services. Certain portions of the Company’s revenues involve a third party in providing goods or services to its customers. In such circumstances, the Company must determine whether the nature of its promise to the customer is to provide the underlying goods or services (the Company is the principal in the transaction and reports the transaction gross) or to arrange for a third party to provide the underlying goods or services (the entity is the agent in the transaction and reports the transaction net). ASC 606 did not change the accounting for the majority of the Company’s revenue arrangements and did not have a material impact to the Company’s consolidated financial statements. The following is a summary of the impact from the adoption of ASC 606: •The majority of the Company’s services are bundled together, and provided and completed for the client on a monthly basis. For these revenue arrangements, the Company continues to recognize revenue on a monthly basis as the client consumes the benefits continuously over time. The timing and recognition of revenues from these arrangements did not change. •Contracts with new clients or with existing clients for new services generally include implementation fees. These fees are recognized in Information processing and software servicing fees when in connection with investment processing platforms and are recognized in Asset management, administration and distribution fees when in connection with investment operations platforms. The Company concluded that most of the current arrangements for implementation services are a distinct and separate performance obligation from the monthly recurring services. The timing and recognition of fees for most of these arrangements have not changed. However, each new revenue arrangement for implementation fees is analyzed to determine whether or not it is a distinct performance obligation. Implementation fees determined not to be a distinct performance obligation would be required to be recognized over the expected life of the client relationship along with the costs relating directly to satisfying such performance obligation. The Company will evaluate each contract in accordance with the requirements of ASC 606. •Research services provided by SIDCO, the Company’s broker-dealer subsidiary, to customers in soft-dollar arrangements were determined to be a separate performance obligation. Research services provided by a broker-dealer may be internally generated or provided by a third party and paid directly by the broker-dealer on the customer’s behalf. It was determined that SIDCO is considered an agent since it does not control the research services before they are transferred to the customer. Therefore, fees received for research services should be recorded in revenues net of amounts paid for the soft-dollar arrangement. These amounts paid by the Company were previously recorded gross as an expense and, beginning January 1, 2018, are recorded net of any revenue recognized. The amounts related to soft-dollar arrangements during the three months ended September 30, 2018 and 2017 were $3,265 and $3,297, respectively. The amounts related to soft-dollar arrangements during the nine months ended September 30, 2018 and 2017 were $10,497 and $10,799, respectively. •Incremental contract acquisition costs related to information processing contracts in the Private Banks segment and investment operations contracts in the Investment Managers segment will be deferred and recognized over the expected client life. These costs primarily consist of sales compensation payments to the Company's sales personnel. As a result, incremental contract acquisition costs are capitalized and subsequently amortized. The Company recorded a cumulative effect adjustment to retained earnings associated with the capitalization of contract costs. For the Company's other sales compensation payments, the Company either applies the practical expedient permitting the expensing of costs to obtain a contract when the expected amortization period is one year or less or there are no contract acquisition costs required to be deferred under the requirements of ASC 606. The Company amortizes deferred contract acquisition costs using the straight-line method.
Cash and Cash Equivalents	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.Cash and Cash EquivalentsCash and cash equivalents includes $286,824 and $401,292 at September 30, 2018 and December 31, 2017, respectively, primarily invested in SEI-sponsored open-ended money market mutual funds. The SEI-sponsored mutual funds are Level 1 assets.
Restricted Cash	Restricted CashRestricted cash includes $3,000 at September 30, 2018 and December 31, 2017 segregated for regulatory purposes related to trade-execution services conducted by SEI Investments (Europe) Limited. Restricted cash also includes $511 and $505 at September 30, 2018 and December 31, 2017, respectively, segregated in special reserve accounts for the benefit of customers of the Company’s broker-dealer subsidiary, SEI Investments Distribution Co. (SIDCO), in accordance with certain rules established by the Securities and Exchange Commission (SEC) for broker-dealers.
Reclassifications	ReclassificationsCertain prior year amounts have been reclassified to conform to current year presentation.
New Accounting Pronouncements	New Accounting Pronouncements In February 2016, the FASB issued ASU No. 2016-02, Leases (ASU 2016-02), as amended, requiring lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases with the exception of short-term leases. For lessees, leases will be classified as either operating or finance leases, with the classification affecting the pattern and classification of expense recognition in the income statement. The updated standard is effective for the Company beginning in the first quarter of 2019. Early adoption is permitted. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (i) its effective date or (ii) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. The Company expects to adopt the new standard on January 1, 2019 and use the effective date as the date of initial application. As a result, financial information will not be updated and the disclosures required under the new standard will not be provided for periods prior to January 1, 2019. The new standard provides a number of optional practical expedients in transition. The Company expects to elect the package of practical expedients which permits the Company to not reassess under the new standard its prior conclusions about lease identification, lease classification and initial direct costs. As part of its project plan’s preliminary assessment and design implementation phases for the adoption of ASU 2016-02, the Company has adopted implementation controls that allow it to properly and timely adopt ASU 2016-02 on the effective date. While the Company continues to assess all of the effects of adoption, the Company believes the most significant effects relate to the recognition of right-of-use assets and lease liabilities on the balance sheet for office space and certain office equipment and providing significant new disclosures about leasing arrangements. The Company owns its corporate headquarters and leases office space in other locations. The Company has completed the process of cataloging existing lease agreements and is currently calculating the right-of-use asset and lease liability. The Company will make updates to the year-end disclosures, with a focus on both status and internal controls over financial reporting. In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13) which requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. ASU 2016-13 becomes effective for the Company during the first quarter of 2020. Early adoption is permitted. The Company is currently evaluating the effect that the updated standard will have on its consolidated financial statements and related disclosures. In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment (ASU 2017-04). The objective of ASU 2017-04 is to simplify the subsequent measurement of goodwill by entities performing their annual goodwill impairment tests by comparing the fair value of a reporting unit, including income tax effects from any tax-deductible goodwill, with its carrying amount and recognizing an impairment charge for the amount by which the carrying amount exceeds fair value. ASU 2017-04 is effective for the Company beginning in the first quarter of 2020. Early adoption is permitted. The Company is currently evaluating the impact of adopting ASU 2017-04 on its consolidated financial statements and related disclosures. In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting (ASU 2018-07) which simplifies the accounting for nonemployee share-based payment transactions. The amendments specify that Topic 718 applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. ASU 2018-07 is effective for the Company beginning in the first quarter of 2019. The Company does not believe the adoption of ASU 2018-07 will have a material impact on its consolidated financial statements and related disclosures. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (ASU 2018-13) which modifies the disclosure requirements on fair value measurements. ASU 2018-13 is effective for the Company beginning in the first quarter of 2020. The Company is currently evaluating the impact of adopting ASU 2018-13 on its consolidated financial statements and related disclosures.
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 interest in the net assets of LSV is reflected in Investment in unconsolidated affiliate on the accompanying Consolidated Balance Sheets and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliate on the accompanying Consolidated Statements of Operations.
Variable Interest Entities	The Company has concluded that it is not the primary beneficiary of the entities and; therefore, is not required to consolidate any of the pooled investment vehicles for which it receives asset management, distribution, administration and custodial fees under the VIE model. The entities either do not meet the definition of a VIE or the Company does not hold a variable interest in the entities. The entities either qualify for the money market scope exception, or are entities in which the Company’s asset management, distribution, administration and custodial fees are commensurate with the services provided and include fair terms and conditions, or are entities that are limited partnerships which have substantive kick-out rights. The Company acts as a fiduciary and does not hold any other interests other than insignificant seed money investments in the pooled investment vehicles. For this reason, the Company also concluded that it is not required to consolidate the pooled investment vehicles under the voting interest entity (VOE) model.
Fair Value of Financial Instruments	The fair value of the Company’s financial assets and liabilities, except for the Company's investment funds sponsored by LSV, 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 open-ended mutual funds that are quoted daily. Level 2 financial assets consist of Government National Mortgage Association (GNMA) mortgage-backed securities held by the Company's wholly-owned limited purpose federal thrift subsidiary, SEI Private Trust Company (SPTC), Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes held by SIDCO. The financial assets held by SIDCO were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The financial assets held by SPTC are debt securities issued by GNMA and are backed by the full faith and credit of the U.S. government. These securities were purchased for the sole purpose of satisfying applicable regulatory requirements and have maturity dates which range from 2021 to 2041. The fair value of the Company's investment funds sponsored by LSV is measured using the net asset value per share (NAV) as a practical expedient. The NAVs of the funds are calculated by the funds' independent custodian and are derived from the fair values of the underlying investments as of the reporting date. The funds allow for investor redemptions at the end of each calendar month. This investment has not been classified in the fair value hierarchy but is presented in the tables below to permit reconciliation to the amounts presented on the accompanying Consolidated Balance Sheets. The valuation of the Company's Level 2 financial assets held by SIDCO and SPTC are based upon securities pricing policies and procedures utilized by third-party pricing vendors. The pricing policies and procedures applied for our Level 1 and Level 2 financial assets during the nine months ended September 30, 2018 were consistent with those as described in our Annual Report on Form 10-K at December 31, 2017. The Company had no Level 3 financial assets at September 30, 2018 or December 31, 2017 that were required to be measured at fair value on a recurring basis.
Investments in Affiliated Funds	The fair value of the Company's investment funds sponsored by LSV is measured using the net asset value per share (NAV) as a practical expedient. The NAVs of the funds are calculated by the funds' independent custodian and are derived from the fair values of the underlying investments as of the reporting date. The funds allow for investor redemptions at the end of each calendar month. This investment has not been classified in the fair value hierarchy but is presented in the tables below to permit reconciliation to the amounts presented on the accompanying Consolidated Balance Sheets.
Available-for-sale Securities	These net unrealized losses are reported as a separate component of Accumulated other comprehensive loss on the accompanying Consolidated Balance Sheets.
Securities Owned	The Company’s broker-dealer subsidiary, SIDCO, has investments in U.S. government agency 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)

9 Months Ended

Sep. 30, 2018

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 have 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 September 30, 2018, the results of operations for the three and nine months ended September 30, 2018 and 2017, and cash flows for the nine-month periods ended September 30, 2018 and 2017. 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, 2017.

The Company adopted the requirements of Accounting Standards Update (ASU) No. 2014-09, Revenue from Contracts with Customers (Topic 606) (Accounting Standards Codification (ASC) 606 (ASC 606)) using the modified retrospective method during the nine months ended September 30, 2018. As a result of the adoption of ASC 606, the Company recorded a cumulative effect adjustment of $14,402 to retained earnings as of January 1, 2018. Prior period information has not been restated (see following caption "Revenue Recognition"). The Company also adopted ASU No. 2016-01, Recognition and Measurement of Financial Assets and Financial Liabilities (see Note 6) and ASU No. 2016-18, Statement of Cash Flows, Restricted Cash (Topic 230) (see following caption "Statements of Cash Flows"). All amounts and disclosures set forth in this Form 10-Q have been updated to comply with the new standards.

Revenue Recognition

Revenue is recognized when the transfer of control of promised goods or services under the terms of a contract with customers are satisfied in an amount that reflects the consideration to which the Company expects to be entitled in exchange for those promised goods or services. Certain portions of the Company’s revenues involve a third party in providing goods or services to its customers. In such circumstances, the Company must determine whether the nature of its promise to the customer is to provide the underlying goods or services (the Company is the principal in the transaction and reports the transaction gross) or to arrange for a third party to provide the underlying goods or services (the entity is the agent in the transaction and reports the transaction net).

ASC 606 did not change the accounting for the majority of the Company’s revenue arrangements and did not have a material impact to the Company’s consolidated financial statements. The following is a summary of the impact from the adoption of ASC 606:

•The majority of the Company’s services are bundled together, and provided and completed for the client on a monthly basis. For these revenue arrangements, the Company continues to recognize revenue on a monthly basis as the client consumes the benefits continuously over time. The timing and recognition of revenues from these arrangements did not change.

•Contracts with new clients or with existing clients for new services generally include implementation fees. These fees are recognized in Information processing and software servicing fees when in connection with investment processing platforms and are recognized in Asset management, administration and distribution fees when in connection with investment operations platforms. The Company concluded that most of the current arrangements for implementation services are a distinct and separate performance obligation from the monthly recurring services. The timing and recognition of fees for most of these arrangements have not changed. However, each new revenue arrangement for implementation fees is analyzed to determine whether or not it is a distinct performance obligation. Implementation fees determined not to be a distinct performance obligation would be required to be recognized over the expected life of the client relationship along with the costs relating directly to satisfying such performance obligation. The Company will evaluate each contract in accordance with the requirements of ASC 606.

•Research services provided by SIDCO, the Company’s broker-dealer subsidiary, to customers in soft-dollar arrangements were determined to be a separate performance obligation. Research services provided by a broker-dealer may be internally generated or provided by a third party and paid directly by the broker-dealer on the customer’s behalf. It was determined that SIDCO is considered an agent since it does not control the research services before they are transferred to the customer. Therefore, fees received for research services should be recorded in revenues net of amounts paid for the soft-dollar arrangement. These amounts paid by the Company were previously recorded gross as an expense and, beginning January 1, 2018, are recorded net of any revenue recognized. The amounts related to soft-dollar arrangements during the three months ended September 30, 2018 and 2017 were $3,265 and $3,297, respectively. The amounts related to soft-dollar arrangements during the nine months ended September 30, 2018 and 2017 were $10,497 and $10,799, respectively.

•Incremental contract acquisition costs related to information processing contracts in the Private Banks segment and investment operations contracts in the Investment Managers segment will be deferred and recognized over the expected client life. These costs primarily consist of sales compensation payments to the Company's sales personnel. As a result, incremental contract acquisition costs are capitalized and subsequently amortized. The Company recorded a cumulative effect adjustment to retained earnings associated with the capitalization of contract costs. For the Company's other sales compensation payments, the Company either applies the practical expedient permitting the expensing of costs to obtain a contract when the expected amortization period is one year or less or there are no contract acquisition costs required to be deferred under the requirements of ASC 606. The Company amortizes deferred contract acquisition costs using the straight-line method.

Cash and Cash Equivalents

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.Cash and Cash EquivalentsCash and cash equivalents includes $286,824 and $401,292 at September 30, 2018 and December 31, 2017, respectively, primarily invested in SEI-sponsored open-ended money market mutual funds. The SEI-sponsored mutual funds are Level 1 assets.

Restricted Cash

Restricted CashRestricted cash includes $3,000 at September 30, 2018 and December 31, 2017 segregated for regulatory purposes related to trade-execution services conducted by SEI Investments (Europe) Limited. Restricted cash also includes $511 and $505 at September 30, 2018 and December 31, 2017, respectively, segregated in special reserve accounts for the benefit of customers of the Company’s broker-dealer subsidiary, SEI Investments Distribution Co. (SIDCO), in accordance with certain rules established by the Securities and Exchange Commission (SEC) for broker-dealers.

Reclassifications

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

New Accounting Pronouncements

In February 2016, the FASB issued ASU No. 2016-02, Leases (ASU 2016-02), as amended, requiring lessees to recognize a right-of-use asset and a lease liability on the balance sheet for all leases with the exception of short-term leases. For lessees, leases will be classified as either operating or finance leases, with the classification affecting the pattern and classification of expense recognition in the income statement. The updated standard is effective for the Company beginning in the first quarter of 2019. Early adoption is permitted. A modified retrospective transition approach is required, applying the new standard to all leases existing at the date of initial application. An entity may choose to use either (i) its effective date or (ii) the beginning of the earliest comparative period presented in the financial statements as its date of initial application. The Company expects to adopt the new standard on January 1, 2019 and use the effective date as the date of initial application. As a result, financial information will not be updated and the disclosures required under the new standard will not be provided for periods prior to January 1, 2019.

The new standard provides a number of optional practical expedients in transition. The Company expects to elect the package of practical expedients which permits the Company to not reassess under the new standard its prior conclusions about lease identification, lease classification and initial direct costs.

As part of its project plan’s preliminary assessment and design implementation phases for the adoption of ASU 2016-02, the Company has adopted implementation controls that allow it to properly and timely adopt ASU 2016-02 on the effective date. While the Company continues to assess all of the effects of adoption, the Company believes the most significant effects relate to the recognition of right-of-use assets and lease liabilities on the balance sheet for office space and certain office equipment and providing significant new disclosures about leasing arrangements. The Company owns its corporate headquarters and leases office space in other locations. The Company has completed the process of cataloging existing lease agreements and is currently calculating the right-of-use asset and lease liability. The Company will make updates to the year-end disclosures, with a focus on both status and internal controls over financial reporting.

In June 2016, the FASB issued ASU No. 2016-13, Financial Instruments-Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments (ASU 2016-13) which requires that expected credit losses relating to financial assets measured on an amortized cost basis and available-for-sale debt securities be recorded through an allowance for credit losses. ASU 2016-13 limits the amount of credit losses to be recognized for available-for-sale debt securities to the amount by which carrying value exceeds fair value and also requires the reversal of previously recognized credit losses if fair value increases. ASU 2016-13 becomes effective for the Company during the first quarter of 2020. Early adoption is permitted. The Company is currently evaluating the effect that the updated standard will have on its consolidated financial statements and related disclosures.

In January 2017, the FASB issued ASU 2017-04, Simplifying the Test for Goodwill Impairment (ASU 2017-04). The objective of ASU 2017-04 is to simplify the subsequent measurement of goodwill by entities performing their annual goodwill impairment tests by comparing the fair value of a reporting unit, including income tax effects from any tax-deductible goodwill, with its carrying amount and recognizing an impairment charge for the amount by which the carrying amount exceeds fair value. ASU 2017-04 is effective for the Company beginning in the first quarter of 2020. Early adoption is permitted. The Company is currently evaluating the impact of adopting ASU 2017-04 on its consolidated financial statements and related disclosures.

In June 2018, the FASB issued ASU 2018-07, Improvements to Nonemployee Share-Based Payment Accounting (ASU 2018-07) which simplifies the accounting for nonemployee share-based payment transactions. The amendments specify that Topic 718 applies to all share-based payment transactions in which a grantor acquires goods or services to be used or consumed in a grantor’s own operations by issuing share-based payment awards. ASU 2018-07 is effective for the Company beginning in the first quarter of 2019. The Company does not believe the adoption of ASU 2018-07 will have a material impact on its consolidated financial statements and related disclosures.

In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (ASU 2018-13) which modifies the disclosure requirements on fair value measurements. ASU 2018-13 is effective for the Company beginning in the first quarter of 2020. The Company is currently evaluating the impact of adopting ASU 2018-13 on its consolidated financial statements and related disclosures.

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 interest in the net assets of LSV is reflected in Investment in unconsolidated affiliate on the accompanying Consolidated Balance Sheets and its interest in the earnings of LSV is reflected in Equity in earnings of unconsolidated affiliate on the accompanying Consolidated Statements of Operations.

Variable Interest Entities

The Company has concluded that it is not the primary beneficiary of the entities and; therefore, is not required to consolidate any of the pooled investment vehicles for which it receives asset management, distribution, administration and custodial fees under the VIE model. The entities either do not meet the definition of a VIE or the Company does not hold a variable interest in the entities. The entities either qualify for the money market scope exception, or are entities in which the Company’s asset management, distribution, administration and custodial fees are commensurate with the services provided and include fair terms and conditions, or are entities that are limited partnerships which have substantive kick-out rights. The Company acts as a fiduciary and does not hold any other interests other than insignificant seed money investments in the pooled investment vehicles. For this reason, the Company also concluded that it is not required to consolidate the pooled investment vehicles under the voting interest entity (VOE) model.

Fair Value of Financial Instruments

The fair value of the Company’s financial assets and liabilities, except for the Company's investment funds sponsored by LSV, 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 open-ended mutual funds that are quoted daily. Level 2 financial assets consist of Government National Mortgage Association (GNMA) mortgage-backed securities held by the Company's wholly-owned limited purpose federal thrift subsidiary, SEI Private Trust Company (SPTC), Federal Home Loan Bank (FHLB) and other U.S. government agency short-term notes held by SIDCO. The financial assets held by SIDCO were purchased as part of a cash management program requiring only short term, top-tier investment grade government and corporate securities. The financial assets held by SPTC are debt securities issued by GNMA and are backed by the full faith and credit of the U.S. government. These securities were purchased for the sole purpose of satisfying applicable regulatory requirements and have maturity dates which range from 2021 to 2041.

The fair value of the Company's investment funds sponsored by LSV is measured using the net asset value per share (NAV) as a practical expedient. The NAVs of the funds are calculated by the funds' independent custodian and are derived from the fair values of the underlying investments as of the reporting date. The funds allow for investor redemptions at the end of each calendar month. This investment has not been classified in the fair value hierarchy but is presented in the tables below to permit reconciliation to the amounts presented on the accompanying Consolidated Balance Sheets.

The valuation of the Company's Level 2 financial assets held by SIDCO and SPTC are based upon securities pricing policies and procedures utilized by third-party pricing vendors.

The pricing policies and procedures applied for our Level 1 and Level 2 financial assets during the nine months ended September 30, 2018 were consistent with those as described in our Annual Report on Form 10-K at December 31, 2017. The Company had no Level 3 financial assets at September 30, 2018 or December 31, 2017 that were required to be measured at fair value on a recurring basis.

Investments in Affiliated Funds

Available-for-sale Securities

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

Securities Owned

The Company’s broker-dealer subsidiary, SIDCO, has investments in U.S. government agency 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.