Short-term Investments (Schedule Of Gross Unrealized Losses And Fair Value Of Investments) (Details) (USD $)	3 Months Ended		12 Months Ended
	Mar. 31, 2012		Dec. 31, 2011
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	$ 72,484,000
Unrealized Losses, Less than 12 Months	(56,000)
Fair Value, 12 Months or Greater	1,855,000
Unrealized Losses, 12 Months or Greater	(8,000)
Fair Value, Total	74,339,000
Available-for-Sale Securities, Gross Unrealized Losses	(64,000)	[1]	(67,000)	[1]
Unrealized loss on securities	100,000		100,000
US Government-sponsored Enterprises Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	19,960,000
Unrealized Losses, Less than 12 Months	(18,000)
Fair Value, 12 Months or Greater	1,855,000
Unrealized Losses, 12 Months or Greater	(8,000)
Fair Value, Total	21,815,000
Available-for-Sale Securities, Gross Unrealized Losses	(26,000)	[1]	(45,000)	[1]
Corporate Debt Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Fair Value, Less than 12 Months	52,524,000
Unrealized Losses, Less than 12 Months	(38,000)
Fair Value, 12 Months or Greater	0
Unrealized Losses, 12 Months or Greater	0
Fair Value, Total	52,524,000
Available-for-Sale Securities, Gross Unrealized Losses	$ (38,000)	[1]	$ (22,000)	[1]

[1] he unrealized gains on investments in available-for-sale securities, net of tax effects were $0.7 million and $0.5 million at March 31, 2012 and December 31, 2011, respectively. Additionally, other comprehensive loss included unrealized losses, net of tax effects of $0.7 million and $1.8 million, on investments underlying our 2001 Non-Qualified Deferred Compensation Plan at March 31, 2012 and December 31, 2011, respectively.