Long-Term Debt (Schedule Of Long-Term Debt) (Details) (USD $)	Mar. 31, 2013		Dec. 31, 2012		Jul. 30, 2012
Debt Instrument [Line Items]
Credit Agreement, amount outstanding	$ 470,000,000		$ 470,000,000
Total long-term debt	766,205,000		766,076,000
Stated interest rate					9.25%
Long-term debt unamortized discount	3,800,000		3,900,000
9.25% Senior Notes due 2020 [Member]
Debt Instrument [Line Items]
Long-term debt	296,205,000	[1]	296,076,000	[1]
Letters Of Credit [Member]
Debt Instrument [Line Items]
Credit Agreement, amount outstanding	$ 23,488,000	[2]	$ 23,488,000	[2]

[1] The amount is net of unamortized discount of $3.8 million and $3.9 million as of March 31, 2013 and December 31, 2012, respectively.

[2] These letters of credit primarily relate to a reclamation deposit requirement. Refer to Note 9 - Commitment and Contingencies for details.