Marketable Securities (Amortized Cost And Estimated Fair Value Of Marketable Securities) (Detail) (USD $)	Sep. 30, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	$ 41,012	$ 80,390
Available-for-Sale, Gross Unrealized Gains	1,956	1,530
Available-for-Sale, Gross Unrealized Losses	130	632
Available-for-Sale, Fair Value	42,838	81,288
Debt Securities Carried By EGL [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	20,399	47,583
Available-for-Sale, Gross Unrealized Gains	252	518
Available-for-Sale, Fair Value	20,651	48,101
Mutual Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	10,650	9,350
Available-for-Sale, Gross Unrealized Gains	544	191
Available-for-Sale, Gross Unrealized Losses	113	603
Available-for-Sale, Fair Value	11,081	8,938
Available-For-Sale Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	9,963	23,457
Available-for-Sale, Gross Unrealized Gains	1,160	821
Available-for-Sale, Gross Unrealized Losses	17	29
Available-for-Sale, Fair Value	11,106	24,249
Available-For-Sale Securities [Member] \| Corporate Bond Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost		1,008
Available-for-Sale, Gross Unrealized Losses		2
Available-for-Sale, Fair Value		1,006
Available-For-Sale Securities [Member] \| Municipal Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost		9,544
Available-for-Sale, Gross Unrealized Gains		9
Available-for-Sale, Fair Value		9,553
Available-For-Sale Securities [Member] \| Other Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost		2,000
Available-for-Sale, Fair Value		2,000
Available-For-Sale Securities [Member] \| Seed Capital Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-Sale, Cost	9,963	10,905
Available-for-Sale, Gross Unrealized Gains	1,160	812
Available-for-Sale, Gross Unrealized Losses	17	27
Available-for-Sale, Fair Value	$ 11,106	$ 11,690

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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