Long-Term Obligations (Schedule Of Long-Term Obligations) (Details) (USD $)	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Debt Instrument [Line Items]
Eurodollar loans under five-year revolving credit agreement bearing annual interest equal to the British Bankers Association LIBOR Rate ("BBA LIBOR") plus an applicable margin based on the Company's consolidated leverage ratio (consolidated funded indebtedness to consolidated EBITDA)	$ 100,000,000	$ 0
Other long-term liabilities	1,710,000	4,497,000
Contingent consideration	21,595,000	0
Unsecured acquisition obligations, net of imputed interest, payable in various installments through 2015	20,996,000	619,000
Total long-term obligations	653,910,000	494,890,000
Less: current installments	397,132,000	619,000
Long-term obligations, excluding current installments	256,778,000	494,271,000
Convertible debt, fixed interest rate	2.75%
Option 2012 [Member]
Debt Instrument [Line Items]
Principal amount of convertible debentures	275,000,000	275,000,000
Unamortized discount	(9,059,000)	(19,273,000)
Convertible debt, fixed interest rate	2.75%	2.75%
Convertible debt, maturity date	2037
Option 2014 [Member]
Debt Instrument [Line Items]
Principal amount of convertible debentures	275,000,000	275,000,000
Unamortized discount	$ (31,332,000)	$ (40,953,000)
Convertible debt, fixed interest rate	2.75%	2.75%
Convertible debt, maturity date	2037