Annual report pursuant to Section 13 and 15(d)

Long-Term Debt (Narrative) (Details)

v2.4.0.6
Long-Term Debt (Narrative) (Details) (USD $)
 12 Months Ended 0 Months Ended 12 Months Ended 1 Months Ended 12 Months Ended
Dec. 31, 2011
Dec. 31, 2009
Dec. 31, 2010
Jun. 10, 2011
8.5% Senior Notes Due June 2019 [Member]
Dec. 31, 2011
8.5% Senior Notes Due June 2019 [Member]
Dec. 31, 2011
8.25% Senior Notes Due June 2014 [Member]
Dec. 31, 2010
8.25% Senior Notes Due June 2014 [Member]
Oct. 31, 2011
Revolving Bank Credit Facility Due May 2015 [Member]
Dec. 31, 2011
Revolving Bank Credit Facility Due May 2015 [Member]
May 05, 2011
Revolving Bank Credit Facility Due May 2015 [Member]
Dec. 31, 2010
Revolving Bank Credit Facility Due May 2015 [Member]
Debt Instrument [Line Items]                      
Aggregate annual maturities of long-term debt, 2012 $ 0                    
Aggregate annual maturities of long-term debt, 2013 0                    
Aggregate annual maturities of long-term debt, 2014 0                    
Aggregate annual maturities of long-term debt, 2015 117,000,000                    
Aggregate annual maturities of long-term debt, thereafter 600,000,000                    
Senior notes 717,000,000   450,000,000 600,000,000 600,000,000   450,000,000   117,000,000     
Senior notes interest rate       8.50% 8.50%   8.25%        
Senior notes maturity date       Jun. 15, 2019 Jun. 01, 2019   Jun. 01, 2014   May 01, 2015    
Senior notes payment terms       semi-annually in arrears on June 15 and December 15 of each year              
Annual effective interest rate 3.70%       8.70%            
Estimated senior notes fair value         612,000,000   441,000,000        
Cost related to repurchase of senior notes           22,000,000          
Write-off of deferred financing costs and other related incidental costs   2,900,000                  
Revolving bank credit facility initial borrowing base                   525,000,000  
Credit agreement expiration date                 May 5, 2015    
Increase to borrowing base               575,000,000      
Common stock and senior note repurchases 100,000,000                    
Restriction on payment of dividends 60,000,000                    
Maximum letter of credit issued 90,000,000                    
Revolving bank credit facility interest rate description Borrowings under the revolving bank credit facility bear interest at the applicable LIBOR plus a margin that varies from 2.00% to 2.75% depending on the level of total borrowings under the Credit Agreement, or an alternative base rate equal to the applicable margin ranging from 1.00% to 1.75% plus the highest of the (a) Prime Rate, (b) Federal Funds Rate plus 0.50%, and (c) LIBOR plus 1.0%.                    
Unused portion of the borrowing base commitment fee 0.50%                    
Unamortized debt issuance cost written off 700,000                    
Revolving bank credit facility amount borrowings 117,000,000                    
Letters of credit     $ 400,000           $ 400,000