Debt (Schedule Of Debt) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012	Feb. 28, 2012	Nov. 30, 2011	Jun. 30, 2011	Nov. 30, 2010
Debt Instrument [Line Items]
LONG-TERM DEBT, NET OF DEBT DISCOUNT	$ 968,663	$ 967,808
Senior Secured Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Line of credit facility amount outstanding	0	0
Eight Point Six Two Five Percent Senior Notes [Member]
Debt Instrument [Line Items]
Senior Notes	600,000	600,000	200,000	200,000	400,000	400,000
Unamortized discount	(4,687)	(4,849)
Seven Point Five Percent Senior Notes [Member]
Debt Instrument [Line Items]
Senior Notes	300,000	300,000
Convertible Senior Notes [Member]
Debt Instrument [Line Items]
Unamortized discount	(400)	(1,093)
Convertible Senior Notes	$ 73,750	$ 73,750