Sale of SEI Asset Korea Sale of SEI Asset Korea (Narrative) (Details) (USD $) In Thousands, unless otherwise specified					3 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2012 SEI Asset Korea Co., Ltd. [Member]
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Percentage of Ownership before Transaction					56.10%
Disposal Group, Including Discontinued Operation, Segment that Includes Disposal Group					Private Banks
Assets	$ 1,309,824	$ 1,294,559			$ 54,783
Cash and Cash Equivalents, at Carrying Value	452,247	420,986	496,292	590,877	48,306
Accrued Income Taxes, Noncurrent					$ 4,815