General (Details 5) (USD $) In Thousands, unless otherwise specified	9 Months Ended	12 Months Ended
Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Short-term and long-term investments
Other-than-temporary unrealized losses	$ 0		$ 0
Realized gains or losses	0	0
Amortized Cost	228,699		233,749
Gross Unrealized Gains	31		70
Gross Unrealized Losses	(152)		(129)
Total, Estimated Fair Value	228,578		233,690
U.S. Government and agency securities
Short-term and long-term investments
Amortized Cost	1,130		1,065
Total, Estimated Fair Value	1,130		1,065
Obligations of government-sponsored enterprises
Short-term and long-term investments
Amortized Cost	8,408		6,126
Gross Unrealized Gains	3		4
Gross Unrealized Losses	(1)		(2)
Total, Estimated Fair Value	8,410		6,128
Corporate debt securities
Short-term and long-term investments
Amortized Cost	218,411		214,603
Gross Unrealized Gains	28		66
Gross Unrealized Losses	(151)		(122)
Total, Estimated Fair Value	218,288		214,547
Taxable municipal bonds
Short-term and long-term investments
Amortized Cost	600		11,805
Gross Unrealized Losses			(5)
Total, Estimated Fair Value	600		11,800
Certificates of deposit
Short-term and long-term investments
Amortized Cost	150		150
Total, Estimated Fair Value	$ 150		$ 150

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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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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- Definition

The amount by which the fair value of an investment in debt and equity securities categorized as Available-for-sale is less than the amortized cost basis or carrying amount of that investment at the balance sheet date and the decline in fair value is deemed to be other than temporary, before considering whether or not such amount is recognized in earnings or other comprehensive income.

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