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	Mar. 31, 2013	Dec. 31, 2012
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	$ 57,539	$ 66,123
Liabilities, Fair Value Disclosure, Recurring	1,458	1,342
Money Market Funds [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	2,387	11,268
Corporate Debt Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	34,168	35,595
U.S. Government Agency Debt Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	19,981	17,251
U.S. Treasury Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	1,003	2,009
Level 1 [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	6,580	17,307
Level 1 [Member] | Money Market Funds [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	2,387	11,268
Level 1 [Member] | Corporate Debt Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	1,451	6,039
Level 1 [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	2,742
Level 2 [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	50,959	48,816
Level 2 [Member] | Corporate Debt Securities [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Fair value of assets measured on a recurring basis	32,717	29,556
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	17,239	17,251
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	1,003	2,009
Level 3 [Member]
Cash, Cash Equivalents And Marketable Securities [Line Items]
Liabilities, Fair Value Disclosure, Recurring	$ 1,458	$ 1,342