Cash, Cash Equivalents And Marketable Securities (Schedule Of Financial Assets Measured At Fair Value On A Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	$ 81,391	$ 134,164
Liabilities, Fair Value Disclosure, Recurring	1,303
Money Market Funds [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	882	12,467
Corporate Debt Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	45,487	73,378
U.S. Government Agency Debt Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	25,350	41,437
U.S. Treasury Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	9,672	6,882
Level 1 [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	882	12,467
Level 1 [Member] | Money Market Funds [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	882	12,467
Level 2 [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	80,509	121,697
Level 2 [Member] | Corporate Debt Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	45,487	73,378
Level 2 [Member] | U.S. Government Agency Debt Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	25,350	41,437
Level 2 [Member] | U.S. Treasury Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	9,672	6,882
Level 3 [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Liabilities, Fair Value Disclosure, Recurring	$ 1,303