v3.5.0.2
Debt - Gain (Loss) on Extinguisment of Debt (Details) - USD ($)
$ in Millions
 3 Months Ended 9 Months Ended
Sep. 30, 2016
Sep. 30, 2015
Sep. 30, 2016
Sep. 30, 2015
Extinguishment of Debt [Line Items]        
Cash Paid in Loss on Extinguishment of Debt $ 178.4   $ 178.4  
Non-cash Loss on Extinguishment of Debt 17.8   17.8  
Total Loss on Extinguishment of Debt 196.2 $ 0.0 196.2 $ 0.0
Non-cash interest expense 7.2   7.2  
$275.7 million 6.09% senior notes due March 2035        
Extinguishment of Debt [Line Items]        
Repayments of long-term debt 93.8   93.8  
Cash Paid in Loss on Extinguishment of Debt 26.1   26.1  
Non-cash Loss on Extinguishment of Debt 8.0   8.0  
Total Loss on Extinguishment of Debt 34.1   34.1  
Non-cash interest expense (1.1)   (1.1)  
$165.2 million 7.40% debentures due September 2035        
Extinguishment of Debt [Line Items]        
Repayments of long-term debt 17.2   17.2  
Cash Paid in Loss on Extinguishment of Debt 7.3   7.3  
Non-cash Loss on Extinguishment of Debt 4.1   4.1  
Total Loss on Extinguishment of Debt 11.4   11.4  
Non-cash interest expense 0.0   0.0  
$650.0 million 6.20% senior notes due March 2040        
Extinguishment of Debt [Line Items]        
Repayments of long-term debt 250.1   250.1  
Cash Paid in Loss on Extinguishment of Debt 85.3   85.3  
Non-cash Loss on Extinguishment of Debt 2.6   2.6  
Total Loss on Extinguishment of Debt 87.9   87.9  
Non-cash interest expense 1.0   1.0  
$600.0 million 5.70% senior notes due May 2041        
Extinguishment of Debt [Line Items]        
Repayments of long-term debt 214.3   214.3  
Cash Paid in Loss on Extinguishment of Debt 59.7   59.7  
Non-cash Loss on Extinguishment of Debt 3.1   3.1  
Total Loss on Extinguishment of Debt 62.8   62.8  
Non-cash interest expense $ 7.3   $ 7.3