Investments in Available-for-Sale Securities (Details) (USD $)	Dec. 31, 2012	Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Continuous Unrealized Loss Position, Fair Value	$ 223,300,000
Available-for-sale Securities, Amortized Cost Basis	240,382,000	5,268,000
Available-for-sale Securities, Gross Unrealized Losses	2,706,000	4,394,000
Available-for-sale Securities, Gross Unrealized Losses	(3,436,000)	(2,122,000)
Available-for-sale Securities, Fair Value Disclosure	239,652,000	7,540,000
Available-for-sale Securities, Debt Securities, Current	234,305,000
US Government Agencies Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	146,993,000
Available-for-sale Securities, Gross Unrealized Losses	2,000
Available-for-sale Securities, Gross Unrealized Losses	(412,000)
Available-for-sale Securities, Fair Value Disclosure	146,583,000
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	88,118,000
Available-for-sale Securities, Gross Unrealized Losses	0
Available-for-sale Securities, Gross Unrealized Losses	(396,000)
Available-for-sale Securities, Fair Value Disclosure	87,722,000
Equity Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Amortized Cost Basis	5,271,000	5,268,000
Available-for-sale Securities, Gross Unrealized Losses	2,704,000	4,394,000
Available-for-sale Securities, Gross Unrealized Losses	(2,628,000)	(2,122,000)
Available-for-sale Securities, Fair Value Disclosure	5,347,000	7,540,000
Short-term Investments [Member]
Schedule of Available-for-sale Securities [Line Items]
Financial Instruments, Owned, Corporate Debt, at Fair Value	87,722,000
Financial Instruments, Owned, US Government and Agency Obligations, at Fair Value	146,583,000
Available-for-sale Securities, Debt Securities, Current	234,305,000
Other Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale Securities, Equity Securities	$ 5,347,000	$ 7,540,000

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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Total of debt securities categorized neither as held-to-maturity nor trading which are intended be sold or mature within one year from the balance sheet date or the normal operating cycle, whichever is longer.

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Amount of equity securities categorized neither as held-to-maturity nor as trading.

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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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The fair value as of the balance sheet date of firm holdings in fixed income or other debt securities issued by a corporation or other issuer not elsewhere specified in the taxonomy. Includes both pledged (to counterparties as collateral for financing transactions) and unpledged holdings.

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