Marketable Securities Amortized Cost and Estimated Fair Value of Marketable Securities (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Schedule Of Marketable Securities [Line Items]
Marketable Securities, Cost	$ 35,166	$ 34,640
Marketable Securities, Gross Unrealized Gains	1,379	1,937
Marketable Securities, Gross Unrealized Losses	153	32
Marketable Securities, Fair Value	36,392	36,545
Debt Securities Carried by EGL [Member]
Schedule Of Marketable Securities [Line Items]
Marketable Securities, Cost	14,762	13,522
Marketable Securities, Gross Unrealized Gains	55	97
Marketable Securities, Gross Unrealized Losses	36	0
Marketable Securities, Fair Value	14,781	13,619
Mutual Funds [Member]
Schedule Of Marketable Securities [Line Items]
Marketable Securities, Cost	7,742	10,946
Marketable Securities, Gross Unrealized Gains	716	412
Marketable Securities, Gross Unrealized Losses	94	12
Marketable Securities, Fair Value	8,364	11,346
Available-for-Sale [Member] \| Securities Investments [Member]
Schedule Of Marketable Securities [Line Items]
Available-for-Sale, Cost	12,662	10,172
Available-for-Sale, Gross Unrealized Gains	608	1,428
Available-for-Sale, Gross Unrealized Losses	23	20
Available-for-Sale, Fair Value	$ 13,247	$ 11,580

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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