Capitalized software development costs in progress associated with future releases.

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Summary of Significant Accounting Policies [Line Items]

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic earnings per share (EPS) or earnings per unit (EPU) in the future that were not included in the computation of diluted EPS or EPU because to do so would increase EPS or EPU amounts or decrease loss per share or unit amounts for the period presented.

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Securities (including those issuable pursuant to contingent stock agreements) that could potentially dilute basic net Income or Loss per outstanding limited partnership unit in the future and that were not included in the computation of diluted net income per limited partnership unit, because to do so would increase net income per unit amounts or decrease loss per unit amounts for the period presented.

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- Definition

Additions made to capitalized computer software costs during the period.

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Amount of expense for amortization of capitalized computer software costs.

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The carrying amount of capitalized computer software costs net of accumulated amortization as of the balance sheet date.

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Amount of cash and cash equivalent. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate.

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Useful life of finite-lived intangible assets, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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Amount of financial support provided to a nonconsolidated legal entity that is required to comply with or operate in accordance with requirements that are similar to those included in Rule 2a-7 of the Investment Company Act of 1940 for registered money market funds.

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Amount of cash and cash equivalent restricted as to withdrawal or usage, classified as current. Cash includes, but is not limited to, currency on hand, demand deposit with financial institution, and account with general characteristic of demand deposit. Cash equivalent includes, but is not limited to, short-term, highly liquid investment that is both readily convertible to known amount of cash and so near maturity that it presents insignificant risk of change in value because of change in interest rate.

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Summary of Significant Accounting Policies - Narrative (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs			$ 22,828	$ 18,414
Net book value of capitalized software	$ 235,559		$ 235,559		$ 236,023
Anti-dilutive employee stock options (in shares)	5,687	10,606	5,744	10,747
Anti-dilutive employee stock options (in USD per share)	$ 66.09	$ 61.06	$ 66.04	$ 61.05
Investment Managers
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs			$ 8,318	$ 7,872
Capitalized software in progress	$ 8,319		8,319
SEI Wealth Platform
Summary of Significant Accounting Policies [Line Items]
Capitalized software development costs			14,510	10,542
Net book value of capitalized software	197,528		197,528
Capitalized software in progress	$ 1,862		1,862
Amortization expense related to the SEI Wealth Platform			$ 21,602	20,517
SEI Wealth Platform \| Weighted Average
Summary of Significant Accounting Policies [Line Items]
Estimated useful life of the SEI Wealth Platform	7 years 8 months 12 days		7 years 8 months 12 days
Investment Managers Platform
Summary of Significant Accounting Policies [Line Items]
Net book value of capitalized software	$ 38,031		$ 38,031
Estimated useful life of the SEI Wealth Platform	7 years		7 years
Amortization expense related to the SEI Wealth Platform			$ 1,100
SEI-Sponsored Open-Ended Money Market Mutual Funds
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents invested in SEI-sponsored money market funds	$ 191,938		191,938		341,311
SEI Investments (Europe) Limited
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents	250		250		250
SEI Investments Distribution Co. (SIDCO)
Summary of Significant Accounting Policies [Line Items]
Cash and cash equivalents	52		52		$ 52
SEI-Sponsored Open-Ended Money Market Mutual Funds
Summary of Significant Accounting Policies [Line Items]
Fees waived	$ 5,397	$ 1,202	$ 14,792	$ 6,764