Derivatives (Schedule Of Interest Rate Swaps) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011	Sep. 30, 2011
Derivative [Line Items]
Estimated fair value of liability	$ 11,170	$ 10,714	$ 13,531
2009 Interest Rate Swap
Derivative [Line Items]
Notional amount	0	0	115,000
Estimated fair value of liability	0	0	13,531
2011 Interest Rate Swap
Derivative [Line Items]
Notional amount	93,500	93,500	0
Estimated fair value of liability	$ 11,170	$ 10,714	$ 0