v2.4.0.8
Debt (Consolidated Debt) (Details) (USD $)
Dec. 31, 2013
Dec. 31, 2012
Debt Instrument [Line Items]    
Long-term Debt $ 2,685,287,000 $ 2,393,408,000
Long-term Debt, Weighted Average Interest Rate 5.20%  
Debt Instrument, Face Amount 2,700,000,000.0 2,400,000,000.0
Revolving Credit Facility [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 0 0
Long-term Debt, Weighted Average Interest Rate 0.00%  
6.45% Notes Due 2014 [Member] | Senior Notes [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 249,971,000 249,905,000
Long-term Debt, Weighted Average Interest Rate 6.30%  
Debt Instrument, Face Amount 250,000,000  
Debt Instrument, Interest Rate, Stated Percentage 6.45%  
5.65% Notes Due 2016 [Member] | Senior Notes [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 251,183,000 251,609,000
Long-term Debt, Weighted Average Interest Rate 5.70%  
Debt Instrument, Face Amount 250,000,000  
Debt Instrument, Interest Rate, Stated Percentage 5.65%  
6.40% Notes Due 2018 [Member] | Senior Notes [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 259,346,000 261,411,000
Long-term Debt, Weighted Average Interest Rate 5.40%  
Debt Instrument, Face Amount 250,000,000  
Debt Instrument, Interest Rate, Stated Percentage 6.40%  
6.55% Notes Due 2019 [Member] | Senior Notes [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 571,515,000 575,065,000
Long-term Debt, Weighted Average Interest Rate 5.70%  
Debt Instrument, Face Amount 550,000,000  
Debt Instrument, Interest Rate, Stated Percentage 6.55%  
4.25% Notes Due 2021 [Member] | Senior Notes [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 557,213,000 558,088,000
Long-term Debt, Weighted Average Interest Rate 4.00%  
Debt Instrument, Face Amount 550,000,000  
Debt Instrument, Interest Rate, Stated Percentage 4.25%  
6.40% Notes Due 2037 [Member] | Senior Notes [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 248,998,000 248,981,000
Long-term Debt, Weighted Average Interest Rate 6.40%  
Debt Instrument, Face Amount 250,000,000  
Debt Instrument, Interest Rate, Stated Percentage 6.40%  
4.20% Notes Due 2042 [Member] | Senior Notes [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 248,377,000 248,349,000
Long-term Debt, Weighted Average Interest Rate 4.20%  
Debt Instrument, Face Amount 250,000,000  
Debt Instrument, Interest Rate, Stated Percentage 4.20%  
5.15% Notes Due 2043 [Member] | Senior Notes [Member]
   
Debt Instrument [Line Items]    
Long-term Debt 298,684,000  
Long-term Debt, Weighted Average Interest Rate 5.20%  
Debt Instrument, Face Amount $ 300,000,000  
Debt Instrument, Interest Rate, Stated Percentage 5.15%