v2.4.0.8
Debt (Consolidated Debt) (Details) (USD $)
Jun. 30, 2014
Dec. 31, 2013
Debt Instrument [Line Items]    
Total debt $ 2,910,496,000 $ 2,685,287,000
Weighted-Average Interest Rate 5.10% [1]  
Debt Instrument, Face Amount 2,900,000,000.0 2,700,000,000.0
Commercial Paper [Member]
   
Debt Instrument [Line Items]    
Total debt 220,977,000 [2] 0 [2]
Weighted-Average Interest Rate 0.30% [1],[2]  
Revolving Credit Facility [Member]
   
Debt Instrument [Line Items]    
Total debt 0 [2] 0 [2]
Weighted-Average Interest Rate 1.30% [1],[2]  
Senior Notes [Member] | 6.45% Notes Due 2014 [Member]
   
Debt Instrument [Line Items]    
Total debt 0 [2] 249,971,000 [2]
Weighted-Average Interest Rate 6.30% [1],[2]  
Debt Instrument, Face Amount 250,000,000.0  
Debt Instrument, Interest Rate, Stated Percentage 6.45%  
Senior Notes [Member] | 5.65% Notes Due 2016 [Member]
   
Debt Instrument [Line Items]    
Total debt 250,970,000 251,183,000
Weighted-Average Interest Rate 5.70% [1]  
Debt Instrument, Face Amount 250,000,000.0  
Debt Instrument, Interest Rate, Stated Percentage 5.65%  
Senior Notes [Member] | 6.40% Notes Due 2018 [Member]
   
Debt Instrument [Line Items]    
Total debt 258,313,000 259,346,000
Weighted-Average Interest Rate 5.40% [1]  
Debt Instrument, Face Amount 250,000,000.0  
Debt Instrument, Interest Rate, Stated Percentage 6.40%  
Senior Notes [Member] | 6.55% Notes Due 2019 [Member]
   
Debt Instrument [Line Items]    
Total debt 569,704,000 571,515,000
Weighted-Average Interest Rate 5.70% [1]  
Debt Instrument, Face Amount 550,000,000.0  
Debt Instrument, Interest Rate, Stated Percentage 6.55%  
Senior Notes [Member] | 4.25% Notes Due 2021 [Member]
   
Debt Instrument [Line Items]    
Total debt 556,763,000 557,213,000
Weighted-Average Interest Rate 4.00% [1]  
Debt Instrument, Face Amount 550,000,000.0  
Debt Instrument, Interest Rate, Stated Percentage 4.25%  
Senior Notes [Member] | 6.40% Notes Due 2037 [Member]
   
Debt Instrument [Line Items]    
Total debt 249,007,000 248,998,000
Weighted-Average Interest Rate 6.40% [1]  
Debt Instrument, Face Amount 250,000,000.0  
Debt Instrument, Interest Rate, Stated Percentage 6.40%  
Senior Notes [Member] | 4.20% Notes Due 2042 [Member]
   
Debt Instrument [Line Items]    
Total debt 248,391,000 248,377,000
Weighted-Average Interest Rate 4.20% [1]  
Debt Instrument, Face Amount 250,000,000.0  
Debt Instrument, Interest Rate, Stated Percentage 4.20%  
Senior Notes [Member] | 5.15% Notes Due 2043 [Member]
   
Debt Instrument [Line Items]    
Total debt 556,371,000 298,684,000
Weighted-Average Interest Rate 5.10% [1]  
Debt Instrument, Face Amount $ 550,000,000.0  
Debt Instrument, Interest Rate, Stated Percentage 5.15%  
[1] Weighted-average interest rate includes the amortization/accretion of discounts, premiums and gains/losses realized on historical cash flow and fair value hedges in interest expense.
[2] These borrowings were outstanding for only a portion of the six month period ending June 30, 2014. The weighted-average interest rate for these borrowings was calculated based on the number of days the borrowings were outstanding during the noted period.