Commitments And Contingencies	9 Months Ended
Sep. 30, 2012
Commitments and Contingencies Disclosure [Abstract]
Commitments And Contingencies	Commitments and Contingencies In the normal course of business, the Company is party to various claims and legal proceedings. One of SEI’s principal subsidiaries, SIDCO, has been named as a defendant in certain putative class action complaints (the Complaints) related to leveraged exchange traded funds (ETFs) advised by ProShares Advisors, LLC. The first complaint was filed on August 5, 2009. To date, the Complaints have been filed in the United States District Court for the Southern District of New York and in the United States District Court for the District of Maryland. The three complaints filed in the District of Maryland have been voluntarily dismissed by the plaintiffs. Two of them were subsequently re-filed in the Southern District of New York. Two of the complaints filed in the Southern District of New York have also been voluntarily dismissed by plaintiffs. The Complaints are purportedly made on behalf of all persons that purchased or otherwise acquired shares in various ProShares leveraged ETFs pursuant or traceable to allegedly false and misleading registration statements, prospectuses and statements of additional information. The Complaints name as defendants ProShares Advisors, LLC; ProShares Trust; ProShares Trust II, SIDCO, and various officers and trustees to ProShares Advisors, LLC; ProShares Trust and ProShares Trust II. The Complaints allege that SIDCO was the distributor and principal underwriter for the various ProShares leveraged ETFs that were distributed to authorized participants and ultimately shareholders. The complaints allege that the registration statements for the ProShares ETFs were materially false and misleading because they failed adequately to describe the nature and risks of the investments. The Complaints allege that SIDCO is liable for these purportedly material misstatements and omissions under Section 11 of the Securities Act of 1933. The Complaints seek unspecified compensatory and other damages, reasonable costs and other relief. Defendants have moved to consolidate the complaints, which motion has been granted. The Court appointed lead plaintiff on July 13, 2010, and an amended consolidated class action complaint was filed on September 25, 2010 asserting substantially the same claims. This complaint subsequently was further amended by the plaintiffs. Defendants moved to dismiss the amended complaint and on September 7, 2012, the District Court for the Southern District of New York issued an opinion dismissing with prejudice the plaintiffs' amended complaint. On October 3, 2012, plaintiffs filed with the Second Circuit Court of Appeals a notice of appeal of the District Court's decision. While the outcome of this litigation is uncertain given its early phase, SEI believes that it has valid defenses to plaintiffs’ claims and intends to defend the lawsuits vigorously. SEI has been named in six lawsuits filed in Louisiana. Five lawsuits were filed in the 19th Judicial District Court for the Parish of East Baton Rouge, State of Louisiana. One of the five actions purports to set forth claims on behalf of a class and also names SPTC as a defendant. Two of the other actions also name SPTC as a defendant. All five actions name various defendants in addition to SEI, and, in all five actions, the plaintiffs purport to bring a cause of action under the Louisiana Securities Act. The putative class action originally included a claim against SEI and SPTC for an alleged violation of the Louisiana Unfair Trade Practices Act. Two of the other five actions include claims for violations of the Louisiana Racketeering Act and possibly conspiracy. In addition, another group of plaintiffs have filed a lawsuit in the 23rd Judicial District Court for the Parish of Ascension, State of Louisiana, against SEI and SPTC and other defendants asserting claims of negligence, breach of contract, breach of fiduciary duty, violations of the uniform fiduciaries law, negligent misrepresentation, detrimental reliance, violations of the Louisiana Securities Act and Louisiana Racketeering Act and conspiracy. The underlying allegations in all the actions are purportedly related to the role of SPTC in providing back-office services to Stanford Trust Company. The petitions allege that SEI and SPTC aided and abetted or otherwise participated in the sale of “certificates of deposit” issued by Stanford International Bank. Two of the five actions filed in East Baton Rouge have been removed to federal court, and plaintiffs’ motions to remand are pending. These two cases have been transferred by the Judicial Panel on Multidistrict Litigation to United States District Court for the Northern District of Texas. On August 31, 2011, the United States District Court for the Northern District of Texas issued an order and judgment that the causes of action alleged against SEI and SPTC in the two remanded actions were preempted by federal law and the Court dismissed these cases with prejudice. The Court of Appeals for the Fifth Circuit granted an expedited appeal of the United States District Court’s order and judgment. The appeal was briefed, and oral argument was held on February 7, 2012. On March 19, 2012, a panel of the Court of Appeals for the Fifth Circuit reversed the decision of the United States District Court and remanded the actions for further proceedings. On April 2, 2012, SEI filed with the United States Court of Appeals for the Fifth Circuit a petition for rehearing en banc of the panel’s opinion. On April 19, 2012, the Fifth Circuit Court of Appeals denied the petition for rehearing. On July 18, 2012, the Company filed a petition for certiorari in the United States Supreme Court, seeking review of the decision by the United States Court of Appeals for the Eleventh Circuit to permit the claims against SEI to proceed. The Company believes that the trial court correctly concluded that the claims against SEI were barred by the federal Securities Litigation Uniform Standards Act and is requesting that the Supreme Court reinstate that dismissal. The case filed in Ascension Parish was also removed to federal court and transferred by the Judicial Panel on Multidistrict Litigation to the Northern District of Texas. The schedule for responding to that complaint has not yet been established. The plaintiffs in the remaining two cases in East Baton Rouge have granted SEI an extension to respond to the filings. SEI and SPTC filed exceptions in the putative class action pending in East Baton Rouge, which the Court granted in part and dismissed the claims under the Louisiana Unfair Trade Practices Act and denied in part as to the other exceptions. SEI and SPTC filed an answer to the East Baton Rouge putative class action; plaintiffs filed a motion for class certification; and SEI and SPTC also filed a motion for summary judgment against certain named plaintiffs which the Court stated will not be set for hearing until after the hearing on the class certification motion. Following the decision by the United States District Court for the Northern District of Texas, the Court in the East Baton Rouge action issued an order staying the proceedings in the East Baton Rouge class action pending the outcome of the appeal of the order and judgment of the United States District Court for the Northern District of Texas. Following the panel opinion of the Court of Appeals on March 19, 2012, the Court in the East Baton Rouge action held a hearing on class certification on September 20, 2012. The Court in the East Baton Rouge action has not yet issued its decision on the class certification motion. While the outcome of this litigation is uncertain given its early phase, SEI and SPTC believe that they have valid defenses to plaintiffs’ claims and intend to defend the lawsuits vigorously. Because of the uncertainty of the make-up of the classes, the specific theories of liability that may survive a motion to dismiss, the lack of discovery regarding damages, causation, mitigation and other aspects that may ultimately bear upon loss, the Company is not reasonably able to provide an estimate of loss, if any, with respect to the foregoing lawsuits.

Commitments and Contingencies

In the normal course of business, the Company is party to various claims and legal proceedings.

One of SEI’s principal subsidiaries, SIDCO, has been named as a defendant in certain putative class action complaints (the Complaints) related to leveraged exchange traded funds (ETFs) advised by ProShares Advisors, LLC. The first complaint was filed on August 5, 2009. To date, the Complaints have been filed in the United States District Court for the Southern District of New York and in the United States District Court for the District of Maryland. The three complaints filed in the District of Maryland have been voluntarily dismissed by the plaintiffs. Two of them were subsequently re-filed in the Southern District of New York. Two of the complaints filed in the Southern District of New York have also been voluntarily dismissed by plaintiffs. The Complaints are purportedly made on behalf of all persons that purchased or otherwise acquired shares in various ProShares leveraged ETFs pursuant or traceable to allegedly false and misleading registration statements, prospectuses and statements of additional information. The Complaints name as defendants ProShares Advisors, LLC; ProShares Trust; ProShares Trust II, SIDCO, and various officers and trustees to ProShares Advisors, LLC; ProShares Trust and ProShares Trust II. The Complaints allege that SIDCO was the distributor and principal underwriter for the various ProShares leveraged ETFs that were distributed to authorized participants and ultimately shareholders. The complaints allege that the registration statements for the ProShares ETFs were materially false and misleading because they failed adequately to describe the nature and risks of the investments. The Complaints allege that SIDCO is liable for these purportedly material misstatements and omissions under Section 11 of the Securities Act of 1933. The Complaints seek unspecified compensatory and other damages, reasonable costs and other relief. Defendants have moved to consolidate the complaints, which motion has been granted. The Court appointed lead plaintiff on July 13, 2010, and an amended consolidated class action complaint was filed on September 25, 2010 asserting substantially the same claims. This complaint subsequently was further amended by the plaintiffs. Defendants moved to dismiss the amended complaint and on September 7, 2012, the District Court for the Southern District of New York issued an opinion dismissing with prejudice the plaintiffs' amended complaint. On October 3, 2012, plaintiffs filed with the Second Circuit Court of Appeals a notice of appeal of the District Court's decision. While the outcome of this litigation is uncertain given its early phase, SEI believes that it has valid defenses to plaintiffs’ claims and intends to defend the lawsuits vigorously.

SEI has been named in six lawsuits filed in Louisiana. Five lawsuits were filed in the 19th Judicial District Court for the Parish of East Baton Rouge, State of Louisiana. One of the five actions purports to set forth claims on behalf of a class and also names SPTC as a defendant. Two of the other actions also name SPTC as a defendant. All five actions name various defendants in addition to SEI, and, in all five actions, the plaintiffs purport to bring a cause of action under the Louisiana Securities Act. The putative class action originally included a claim against SEI and SPTC for an alleged violation of the Louisiana Unfair Trade Practices Act. Two of the other five actions include claims for violations of the Louisiana Racketeering Act and possibly conspiracy. In addition, another group of plaintiffs have filed a lawsuit in the 23rd Judicial District Court for the Parish of Ascension, State of Louisiana, against SEI and SPTC and other defendants asserting claims of negligence, breach of contract, breach of fiduciary duty, violations of the uniform fiduciaries law, negligent misrepresentation, detrimental reliance, violations of the Louisiana Securities Act and Louisiana Racketeering Act and conspiracy. The underlying allegations in all the actions are purportedly related to the role of SPTC in providing back-office services to Stanford Trust Company. The petitions allege that SEI and SPTC aided and abetted or otherwise participated in the sale of “certificates of deposit” issued by Stanford International Bank. Two of the five actions filed in East Baton Rouge have been removed to federal court, and plaintiffs’ motions to remand are pending. These two cases have been transferred by the Judicial Panel on Multidistrict Litigation to United States District Court for the Northern District of Texas. On August 31, 2011, the United States District Court for the Northern District of Texas issued an order and judgment that the causes of action alleged against SEI and SPTC in the two remanded actions were preempted by federal law and the Court dismissed these cases with prejudice. The Court of Appeals for the Fifth Circuit granted an expedited appeal of the United States District Court’s order and judgment. The appeal was briefed, and oral argument was held on February 7, 2012. On March 19, 2012, a panel of the Court of Appeals for the Fifth Circuit reversed the decision of the United States District Court and remanded the actions for further proceedings. On April 2, 2012, SEI filed with the United States Court of Appeals for the Fifth Circuit a petition for rehearing en banc of the panel’s opinion. On April 19, 2012, the Fifth Circuit Court of Appeals denied the petition for rehearing. On July 18, 2012, the Company filed a petition for certiorari in the United States Supreme Court, seeking review of the decision by the United States Court of Appeals for the Eleventh Circuit to permit the claims against SEI to proceed. The Company believes that the trial court correctly concluded that the claims against SEI were barred by the federal Securities Litigation Uniform Standards Act and is requesting that the Supreme Court reinstate that dismissal.

The case filed in Ascension Parish was also removed to federal court and transferred by the Judicial Panel on Multidistrict Litigation to the Northern District of Texas. The schedule for responding to that complaint has not yet been established. The plaintiffs in the remaining two cases in East Baton Rouge have granted SEI an extension to respond to the filings. SEI and SPTC filed exceptions in the putative class action pending in East Baton Rouge, which the Court granted in part and dismissed the claims under the Louisiana Unfair Trade Practices Act and denied in part as to the other exceptions. SEI and SPTC filed an answer to the East Baton Rouge putative class action; plaintiffs filed a motion for class certification; and SEI and SPTC also filed a motion for summary judgment against certain named plaintiffs which the Court stated will not be set for hearing until after the hearing on the class certification motion. Following the decision by the United States District Court for the Northern District of Texas, the Court in the East Baton Rouge action issued an order staying the proceedings in the East Baton Rouge class action pending the outcome of the appeal of the order and judgment of the United States District Court for the Northern District of Texas. Following the panel opinion of the Court of Appeals on March 19, 2012, the Court in the East Baton Rouge action held a hearing on class certification on September 20, 2012. The Court in the East Baton Rouge action has not yet issued its decision on the class certification motion. While the outcome of this litigation is uncertain given its early phase, SEI and SPTC believe that they have valid defenses to plaintiffs’ claims and intend to defend the lawsuits vigorously.

Because of the uncertainty of the make-up of the classes, the specific theories of liability that may survive a motion to dismiss, the lack of discovery regarding damages, causation, mitigation and other aspects that may ultimately bear upon loss, the Company is not reasonably able to provide an estimate of loss, if any, with respect to the foregoing lawsuits.