Long-Term Obligations (Schedule Of Debt And Equity Components For Convertible Debentures) (Details) (USD $)	Mar. 31, 2012	Dec. 31, 2011	Oct. 31, 2007
2.75% Series A [Member]
Debt Instrument [Line Items]
Principal amount of convertible debentures	$ 275,000,000	$ 275,000,000	$ 275,000,000
Unamortized discount	(6,395,000)	(9,059,000)
Net carrying amount	268,605,000	265,941,000
Additional paid-in capital	29,065,000	29,065,000
2.75% Series B [Member]
Debt Instrument [Line Items]
Principal amount of convertible debentures	275,000,000	275,000,000	275,000,000
Unamortized discount	(28,817,000)	(31,332,000)
Net carrying amount	246,183,000	243,668,000
Additional paid-in capital	$ 41,238,000	$ 41,238,000