Marketable Securities (Amortized Cost And Estimated Fair Value Of Marketable Securities) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2011	Dec. 31, 2010
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	$ 80,390	$ 89,985
Available-for-Sale, Gross Unrealized Gains	1,530	2,903
Available-for-Sale, Gross Unrealized Losses	632	58
Available-for-Sale, Fair Value	81,288	92,830
Available-For-Sale [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	23,457	39,148
Available-for-Sale, Gross Unrealized Gains	821	2,402
Available-for-Sale, Gross Unrealized Losses	29	40
Available-for-Sale, Fair Value	24,249	41,510
Corporate Bonds [Member] \| Available-For-Sale [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	1,008	7,126
Available-for-Sale, Gross Unrealized Gains		45
Available-for-Sale, Gross Unrealized Losses	2
Available-for-Sale, Fair Value	1,006	7,171
Municipal Bonds [Member] \| Available-For-Sale [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	9,544	16,910
Available-for-Sale, Gross Unrealized Gains	9	107
Available-for-Sale, Gross Unrealized Losses		15
Available-for-Sale, Fair Value	9,553	17,002
Other Debt Securities [Member] \| Available-For-Sale [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	2,000	1,000
Available-for-Sale, Fair Value	2,000	1,000
Seed Capital Investments [Member] \| Available-For-Sale [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	10,905	14,112
Available-for-Sale, Gross Unrealized Gains	812	2,250
Available-for-Sale, Gross Unrealized Losses	27	25
Available-for-Sale, Fair Value	11,690	16,337
Debt Securities Carried By EGL [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	47,583	50,837
Available-for-Sale, Gross Unrealized Gains	518	501
Available-for-Sale, Gross Unrealized Losses		18
Available-for-Sale, Fair Value	48,101	51,320
Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	9,350
Available-for-Sale, Gross Unrealized Gains	191
Available-for-Sale, Gross Unrealized Losses	603
Available-for-Sale, Fair Value	$ 8,938

This item represents the cost of debt and equity securities, which are categorized neither as held-to-maturity nor trading, net of adjustments including accretion, amortization, collection of cash, previous other-than-temporary impairments recognized in earnings (less any cumulative-effect adjustments recognized, as defined), and fair value hedge accounting adjustments, if any.

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This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission. This item represents Available-for-sale Securities which consist of all investments in certain debt and equity securities neither classified as trading or held-to-maturity securities. A debt security represents a creditor relationship with an enterprise. Debt securities include, among other items, US Treasury securities, US government securities, municipal securities, corporate bonds, convertible debt, commercial paper, and all securitized debt instruments. An equity security represents an ownership interest in an enterprise or the right to acquire or dispose of an ownership interest in an enterprise at fixed or determinable prices. Equity securities include, among other things, common stock, certain preferred stock, warrant rights, call options, and put options, but do not include convertible debt. An entity may opt to provide the reader with additional narrative text to better understand the nature of investments in debt and equity securities which are categorized as Available-for-sale.

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- Definition

This item represents the gross unrealized gains for securities, at a point in time, which are categorized neither as held-to-maturity nor trading securities.

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