Cash, Cash Equivalents And Marketable Securities (Summary Of Cash, Cash Equivalents, And Marketable Securities) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	$ 72,857	$ 77,839
Available-for-sale securities, Gross Unrealized Gains	34	55
Available-for-sale securities, Gross Unrealized Losses	(2)	(2)
Available-for-sale securities	72,889	77,892
Total available-for-sale securities, Amortized Cost	50,927	48,763
Total available-for-sale securities, Gross Unrealized Gains	34	55
Total available-for-sale securities, Gross Unrealized Losses	(2)	(2)
Total available-for-sale securities	50,959	48,816
Cash and Cash Equivalents [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	21,930	29,076
Available-for-sale securities	21,930	29,076
Corporate Debt Securities [Member] \| Maturing Within One Year [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	26,160	21,662
Available-for-sale securities, Gross Unrealized Gains	21	31
Available-for-sale securities, Gross Unrealized Losses	(1)
Available-for-sale securities	26,180	21,693
Corporate Debt Securities [Member] \| Maturing Between One And Two Years [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	6,533	7,858
Available-for-sale securities, Gross Unrealized Gains	4	7
Available-for-sale securities, Gross Unrealized Losses	(1)	(2)
Available-for-sale securities	6,536	7,863
U.S. Government Agency Debt Securities [Member] \| Maturing Within One Year [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	17,230	14,027
Available-for-sale securities, Gross Unrealized Gains	9	8
Available-for-sale securities	17,239	14,035
U.S. Government Agency Debt Securities [Member] \| Maturing Between One And Two Years [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost		3,208
Available-for-sale securities, Gross Unrealized Gains		8
Available-for-sale securities		3,216
U.S. Treasury Securities [Member] \| Maturing Within One Year [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	1,004	2,008
Available-for-sale securities, Gross Unrealized Gains		1
Available-for-sale securities	1,004	2,009
Cash [Member] \| Cash and Cash Equivalents [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	15,350	11,769
Available-for-sale securities	15,350	11,769
Money Market Funds [Member] \| Cash and Cash Equivalents [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	2,387	11,268
Available-for-sale securities	2,387	11,268
Corporate Debt Securities [Member] \| Cash and Cash Equivalents [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	1,451	6,039
Available-for-sale securities	1,451	6,039
U.S. Government Agency Debt Securities [Member] \| Cash and Cash Equivalents [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Available-for-sale securities, Amortized Cost	2,742
Available-for-sale securities	$ 2,742

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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