Quarterly report pursuant to Section 13 or 15(d)

Debt - (Interest Rate Swaps) (Details)

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Debt - (Interest Rate Swaps) (Details) - USD ($)
Sep. 30, 2017
Feb. 28, 2017
Nov. 30, 2016
Interest Rate Swap      
Debt Instrument [Line Items]      
Notional amount of interest rate swap agreements $ 2,700,000,000    
Average variable rate, interest rate swap agreements (percent) 3.61%    
Weighted average rate, interest rate swap agreements (percent) 4.91%    
February 15, 2021 Interest Rate Swap      
Debt Instrument [Line Items]      
Notional amount of interest rate swap agreements $ 600,000,000    
May 15, 2022 Expiration, Interest Rate Swap      
Debt Instrument [Line Items]      
Notional amount of interest rate swap agreements 500,000,000    
February 15, 2024 Expiration Interest Rate Swap      
Debt Instrument [Line Items]      
Notional amount of interest rate swap agreements 1,000,000,000    
January 15, 2025 Expiration Interest Rate Swap      
Debt Instrument [Line Items]      
Notional amount of interest rate swap agreements 600,000,000 $ 600,000,000  
Average variable rate, interest rate swap agreements (percent)   2.53%  
Senior Notes | $1,200 million 4.75% Senior notes, due January 15, 2025      
Debt Instrument [Line Items]      
Debt, face amount $ 1,200,000,000   $ 1,200,000,000
Interest rate, stated 4.75%   4.75%