Derivatives (Schedule Of Interest Rate Swaps) (Details) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012	Dec. 31, 2011	Jun. 30, 2011
Derivative [Line Items]
Estimated fair value of liability	$ 11,020	$ 10,714	$ 9,800
2009 Interest Rate Swap
Derivative [Line Items]
Notional amount	0	0	115,000
Estimated fair value of liability	0	0	9,800
2011 Interest Rate Swap
Derivative [Line Items]
Notional amount	93,500	93,500	0
Estimated fair value of liability	$ 11,020	$ 10,714	$ 0