Marketable Securities (Investments Available For Sale) (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Debt Securities, Available-for-sale [Line Items]
Equity securities, FV-NI	$ 5,533	$ 4,887
Investments Available for sale, Cost Amount	100,578	114,398
Investments Available for sale, Gross Unrealized Gains	1,413	126
Investments Available for sale, Gross Unrealized (Losses)	(411)	(2,623)
Investments Available for sale, Fair Value	101,580	111,901
SEI-sponsored mutual funds
Debt Securities, Available-for-sale [Line Items]
Equity securities, FV-NI, Cost Amount	7,477	7,446
Equity securities, FV-NI, Gross Unrealized Gains	105	0
Equity securities, FV-NI, Gross Unrealized (Losses)	(411)	(788)
Equity securities, FV-NI	7,171	6,658
Equities and other mutual funds
Debt Securities, Available-for-sale [Line Items]
Equity securities, FV-NI, Cost Amount	3,476	3,434
Equity securities, FV-NI, Gross Unrealized Gains	666	126
Equity securities, FV-NI, Gross Unrealized (Losses)	0	0
Equity securities, FV-NI	4,142	3,560
Fixed income securities
Debt Securities, Available-for-sale [Line Items]
Debt securities, Cost Amount	89,625	103,518
Debt securities, Gross Unrealized Gains	642	0
Debt securities, Gross Unrealized (Losses)	0	(1,835)
Debt securities, Fair Value	$ 90,267	$ 101,683

Debt Securities, Available-For-Sale And Equity Securities, FV-NI

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Debt Securities, Available-For-Sale And Equity Securities, FV-NI, Accumulated Gross Unrealized Gain, Before Tax

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No definition available.

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Debt Securities, Available-For-Sale And Equity Securities, FV-NI, Accumulated Gross Unrealized Loss, Before Tax

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Debt Securities, Available-For-Sale And Equity Securities, FV-NI, Cost

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Equity Securities, FV-NI, Accumulated Gross Unrealized Gain, Before Tax

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Equity Securities, FV-NI, Accumulated Gross Unrealized Loss, Before Tax

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- Definition

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

+ References

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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