Accumulated appreciation or loss, net of tax, in value of the total of available-for-sale securities at the end of an accounting period.

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Date of maturity of a debt security categorized as neither trading nor held-to-maturity, in CCYY-MM-DD format.

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This item represents the difference between the gross realized gains and losses realized on the sale of debt or equity securities categorized neither as held-to-maturity nor trading securities. Additionally, this item would include any losses recognized for other than temporary impairments (OTTI) of the subject investments in debt and equity securities.

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This item represents the tax effects occurring during the period which are related to the net unrealized gain (loss) resulting from changes in the fair [carrying] value during the period of available-for-sale securities. Such tax affects would have been charged or credited directly to other comprehensive income or to related components of shareholders' equity.

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The fair value as of the balance sheet date of firm holdings in debt obligations issued by the US government including short-term Treasury bills, medium-term Treasury notes, and long-term Treasury bonds, as well as debt issued by agencies. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

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All other debt and equity financial instruments, which aren't categorized as available-for-sale, or held-to-maturity and which are not otherwise listed in the existing taxonomy, intended to be held longer than one year from the balance sheet date or the normal operating cycle, if longer.

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The net realized gains or losses on investments during the period, not including gains or losses on securities separately or otherwise categorized as trading, available-for-sale, or held-to-maturity.

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This item represents the gain (loss) realized during the period from the sale of trading securities.

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Marketable Securities (Narrative) (Details) (USD $)	3 Months Ended		12 Months Ended
Marketable Securities (Narrative) (Details) (USD $)	Mar. 31, 2013	Mar. 31, 2012	Dec. 31, 2012
Schedule of Investments [Line Items]
Net unrealized holding gains	$ 2,729,000		$ 2,829,000
Unrealized holding gains during the period, income tax expense	1,394,000		1,554,000
Available-for-sale Securities, Gross Realized Gain (Loss)	0	0
Investments in LSV-sponsored funds	5,853,000		5,909,000
Securities owned	21,107,000		20,088,000
SEI Private Trust Company [Member] \| Minimum [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, Date	Dec. 15, 2020
SEI Private Trust Company [Member] \| Maximum [Member]
Schedule of Investments [Line Items]
Available-for-sale Securities, Debt Maturities, Date	Mar. 20, 2043
U.S. Government Agency And Commercial Paper Securities [Member]
Schedule of Investments [Line Items]
Realized Investment Gains (Losses)	0	0
SIV Securities [Member]
Schedule of Investments [Line Items]
Trading Securities, Realized Gain (Loss)		2,882,000
LSV-Sponsored Mutual Funds [Member]
Schedule of Investments [Line Items]
Investments in LSV-sponsored funds	4,691,000		4,706,000
Trading Securities, Realized Gain (Loss)	$ 0	$ 0