Summary Of Significant Accounting Policies (Narrative) (Details) (USD $) In Thousands, except Share data, unless otherwise specified | 3 Months Ended | 9 Months Ended | ||||
|---|---|---|---|---|---|---|
Sep. 30, 2011 | Sep. 30, 2010 | Sep. 30, 2011 | Sep. 30, 2010 | Dec. 31, 2010 | Dec. 31, 2009 | |
| Cash and cash equivalents | $ 428,865 | $ 451,778 | $ 428,865 | $ 451,778 | $ 496,292 | $ 590,877 |
| Capitalized software development costs for software sold to customers during period | 30,556 | 28,097 | ||||
| Capitalized software, weighted average remaining life, years | 10.7 | |||||
| Amortization expense related to capitalized software | 19,299 | 17,149 | ||||
| Capitalized software, accumulated amortization | 110,246 | 110,246 | 90,947 | |||
| Anti-dilutive employee stock options | 16,290,000 | 9,810,000 | 13,273,000 | 16,096,000 | ||
| Average exercise price of anti-dilutive employee stock options | $ 23.66 | $ 25.53 | $ 24.72 | $ 23.47 | ||
Global Wealth Platform [Member] | ||||||
| Capitalized software, weighted average remaining life, years | 10.8 | |||||
| Amortization expense related to capitalized software | 18,873 | 16,724 | ||||
| Net book value of GWP | 289,683 | 289,683 | ||||
| Capitalized software, accumulated amortization | 81,025 | 81,025 | ||||
| Capitalized software development costs in-progress associated with future releases | 14,895 | |||||
| Software development cost useful life, years | 15 | |||||
SEI-Sponsored Open-Ended Money Market Mutual Funds [Member] | ||||||
| Cash and cash equivalents | 283,461 | 283,461 | 383,946 | |||
SEI Investments Distribution Co (SIDCO) [Member] | ||||||
| Restricted cash | 1,000 | 1,000 | 1,000 | |||
SEI Investments (Europe) Limited [Member] | ||||||
| Restricted cash | $ 3,000 | $ 3,000 | $ 3,000 | |||
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- Definition Average exercise price of employee stock options outstanding that were excluded from the computation of diluted earnings per share because the effect would have been anti-dilutive.
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- Definition Capitalized software development costs for software sold to customers during period.
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- Definition Capitalized Software Development Costs In-Progress Associated with Future Releases Summary of Significant Accounting Policies
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- Definition Capitalized Software, Weighted Average Remaining Life
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- Definition Software development cost useful life
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- Definition 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. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition For each balance sheet presented, the amount of accumulated amortization for capitalized computer software costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition For each income statement presented, the amount charged to expense for amortization of capitalized computer software costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The gross amount of capitalized computer software costs as of the balance sheet date. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition 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 Entity 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. Compensating balance arrangements that do not legally restrict the withdrawal or usage of cash amounts may be reported as Cash and Cash Equivalents, while legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or company statements of intention with regard to particular deposits are not generally reported as cash and cash equivalents. Includes cash and cash equivalents associated with the entity's continuing operations. Excludes cash and cash equivalents associated with the disposal group (and discontinued operation). Reference 1: http://www.xbrl.org/2003/role/presentationRef
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- Definition The carrying amounts of cash and cash equivalent items which are restricted as to withdrawal or usage. Restrictions may include legally restricted deposits held as compensating balances against borrowing arrangements, contracts entered into with others, or entity statements of intention with regard to particular deposits; however, time deposits and short-term certificates of deposit are not generally included in legally restricted deposits. Excludes compensating balance arrangements that are not agreements which legally restrict the use of cash amounts shown on the balance sheet. This element is for unclassified presentations; for classified presentations there is a separate and distinct element. Reference 1: http://www.xbrl.org/2003/role/presentationRef
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