Fair Value Measurements (Schedule Of Fair Value Of Debt) (Details) (USD $) In Thousands, unless otherwise specified	May 31, 2012	Jun. 30, 2012 Fixed-Rate Debt [Member]	Dec. 31, 2011 Fixed-Rate Debt [Member]	Jun. 30, 2012 Variable-Rate Debt [Member]	Dec. 31, 2011 Variable-Rate Debt [Member]	Jun. 30, 2012 Significant Unobservable Inputs (Level 3) [Member] Fixed-Rate Debt [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member] Fixed-Rate Debt [Member]	Jun. 30, 2012 Significant Unobservable Inputs (Level 3) [Member] Variable-Rate Debt [Member]	Dec. 31, 2011 Significant Unobservable Inputs (Level 3) [Member] Variable-Rate Debt [Member]
Fair Value Measurements [Line Items]
Carrying value	$ 115,000	$ 1,819,541	$ 2,014,834
Carrying value				375,144	517,003
Fair value						$ 1,958,305	$ 2,054,670	$ 388,486	$ 531,353