Debt (Components Of Debt) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Debt Instrument [Line Items]
Short-term debt	$ 1,200	$ 1,200
Variable rate (1.644% and 2.200% at December 31, 2013 and December 31, 2012, respectively) Credit Facility, expires December 2018	282,900
Unamortized discount	(1,004)	(1,127)
Long-term debt	1,950,096	1,668,273
Total debt	1,951,296	1,669,473
Variable interest rate	1.64%	2.20%
7.15% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Short-term debt	1,200	1,200
Stated interest rate	7.15%	7.15%
7.35% Senior Notes due 2017 [Member]
Debt Instrument [Line Items]
Senior Notes	15,000	15,000
Stated interest rate	7.35%	7.35%
7.125% Senior Notes due 2017 [Member]
Debt Instrument [Line Items]
Senior Notes	25,000	25,000
Stated interest rate	7.125%	7.125%
7.15% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Senior Notes	28,200	29,400
Stated interest rate	7.15%	7.15%
7.5% Senior Notes due 2018 [Member]
Debt Instrument [Line Items]
Senior Notes	600,000	600,000
Stated interest rate	7.50%	7.50%
4.10% Senior Notes Due 2022 [Member]
Debt Instrument [Line Items]
Senior Notes	$ 1,000,000	$ 1,000,000
Stated interest rate	4.10%	4.10%