Fair Value Of Assets And Liabilities (Schedule Of Estimated Fair Values Of Assets And Liabilities Not Measured On Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Convertible debt, fixed interest rate	2.75%
2.75% Series A [Member]
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Convertible debt, fixed interest rate	2.75%
2.75% Series B [Member]
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Convertible debt, fixed interest rate	2.75%
Carrying Value [Member]
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Short-term investments - held to maturity	$ 20,000	$ 20,000
Short-term debt	170,000	100,000
Deferred acquisition obligations	18,855	20,996
Carrying Value [Member] | 2.75% Series A [Member]
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Debentures	268,605	265,941
Carrying Value [Member] | 2.75% Series B [Member]
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Debentures	246,183	243,668
Fair Value [Member]
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Short-term investments - held to maturity	20,000	20,000
Short-term debt	170,000	100,000
Deferred acquisition obligations	18,855	20,996
Fair Value [Member] | 2.75% Series A [Member]
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Debentures	283,250	281,188
Fair Value [Member] | 2.75% Series B [Member]
Fair Value, Assets and Liabilities Measured On Nonrecurring Basis [Line Items]
Debentures	$ 304,734	$ 300,781