Derivative Instruments And Hedging Activities (Schedule Of Notional Values And Fair Values Of Derivative Instruments) (Details) (Cash Flow Interest Rate Contracts [Member], Designated As Hedging Instrument [Member], USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Cash Flow Interest Rate Contracts [Member] | Designated As Hedging Instrument [Member]
Notional Value	$ 642,134	$ 761,907
Asset derivatives, Positive fair value
Liability derivatives, Negative fair value	$ (22,455)	$ (24,877)