Debt (Summary Of Long-Term Debt) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Long-term debt	$ 1,834,500	$ 1,685,897
Less current portion	20,000	810
Long-term debt, noncurrent	1,814,500	1,685,087
Revolving Credit Facility, Interest Payable Monthly At Floating Rate, Due December 2017 [Member]
Debt Instrument [Line Items]
Long-term debt		75,000
Term Loan, Interest Payable Monthly At Floating Rate And Principal Payable Quarterly, Due December 2017 [Member]
Debt Instrument [Line Items]
Long-term debt	385,000
U.S. Government Guaranteed Long-term Financing, Interest Payable Semiannually At 6.45%, Due In Semiannual Installments Through June 2027 [Member]
Debt Instrument [Line Items]
Long-term debt		12,546
Senior Notes, Interest Payable Semiannually At 6 7/8%, Due June 2014 [Member]
Debt Instrument [Line Items]
Long-term debt	150,000	300,000
Discount On 6 7/8% Senior Notes [Member]
Debt Instrument [Line Items]
Long-term debt	(500)	(1,649)
Senior Notes, Interest Payable Semiannually At 6 3/8%, Due May 2019 [Member]
Debt Instrument [Line Items]
Long-term debt	500,000	500,000
Senior Notes, Interest Payable Semiannually At 7 1/8%, Due December 2021 [Member]
Debt Instrument [Line Items]
Long-term debt	$ 800,000	$ 800,000