Fair Value (Assets And Liabilities Measured At Fair Value) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Level 1 [Member]	Dec. 31, 2011 Level 1 [Member]	Mar. 31, 2013 Level 2 [Member]	Dec. 31, 2011 Level 2 [Member]	Mar. 31, 2013 Level 3 [Member]	Dec. 31, 2011 Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Money market demand accounts and investment grade fixed income securities	$ 232,500	$ 60,400	$ 232,539	$ 60,425	$ 0	$ 0	$ 0	$ 0
Short-term Investments	$ 53,000	$ 0	$ 0		$ 53,000		$ 0