Investments in Debt Securities (Detail) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 20,745,938	$ 24,850,448
Gross Unrealized Gain	15,479	11,032
Gross Unrealized Loss	(1,367)	(4,694)
Fair Value	20,760,050	24,856,786
Marketable securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,835,995	15,419,577
Gross Unrealized Gain	9,207	6,462
Gross Unrealized Loss	(7)	(4,603)
Fair Value	10,845,195	15,421,436
Marketable securities \| U.S. Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,000,897	8,373,355
Gross Unrealized Gain	353	3,126
Gross Unrealized Loss	(7)	(233)
Fair Value	2,001,243	8,376,248
Marketable securities \| Corporate and other debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,835,098	7,046,222
Gross Unrealized Gain	8,854	3,336
Gross Unrealized Loss		(4,370)
Fair Value	8,843,952	7,045,188
Long-term marketable securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,909,943	9,430,871
Gross Unrealized Gain	6,272	4,570
Gross Unrealized Loss	(1,360)	(91)
Fair Value	9,914,855	9,435,350
Long-term marketable securities \| U.S. Government and agency securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	5,198,264	8,399,428
Gross Unrealized Gain	2,747	2,223
Gross Unrealized Loss		(91)
Fair Value	5,201,011	8,401,560
Long-term marketable securities \| Corporate and other debt securities
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,711,679	1,031,443
Gross Unrealized Gain	3,525	2,347
Gross Unrealized Loss	(1,360)
Fair Value	$ 4,713,844	$ 1,033,790

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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