Derivative Instruments And Hedging (Notional Amount Of Forward Fixed Interest Rate Swap Agreements To Manage Variable Interest Obligations) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Currency sold	$ 150,000	$ 120,637
Notional amount of interest rate swaps	160,000	80,000
Euro [Member]
Currency sold	75,404	59,360
British Pound [Member]
Currency sold	24,767	21,144
Canadian Dollar [Member]
Currency sold	25,642	21,776
Australian Dollar [Member]
Currency sold	10,700	7,930
Japanese Yen [Member]
Currency sold	13,487	10,427
Swiss Franc [Member]
Currency purchased	$ 20,631	$ 12,542