Annual report pursuant to Section 13 and 15(d)

Long-term Debt (Details)

v3.8.0.1
Long-term Debt (Details)
12 Months Ended
Sep. 13, 2016
USD ($)
Dec. 31, 2017
USD ($)
Dec. 31, 2016
USD ($)
Long-term debt      
Net unamortized debt issuance costs   $ (9,000,000) $ (10,086,000)
Long-term debt, net   1,196,000,000 849,914,000
Revolving credit facility      
Long-term debt      
Long-term debt   555,000,000 $ 210,000,000
Maximum borrowing capacity   $ 1,500,000,000  
Weighted average interest rate (as a percent)   2.81% 2.23%
Letter of credit      
Long-term debt      
Outstanding letters of credit   $ 0 $ 0
Margin rates   25  
Letter of credit | Minimum      
Long-term debt      
Commitment fees on the unused portion (as a percent)   0.25%  
Commitment fees on the unused portion during investment grade period (as a percent)   0.175%  
Letter of credit | Maximum      
Long-term debt      
Commitment fees on the unused portion (as a percent)   0.375%  
Commitment fees on the unused portion during investment grade period (as a percent)   0.375%  
5.375% Senior Notes due 2024      
Long-term debt      
Long-term debt   $ 650,000,000 $ 650,000,000
Face amount $ 650,000,000    
Interest rate (as a percent) 5.375%    
Debt instrument redemption percentage upon change of control 101.00%    
5.375% Senior Notes due 2024 | Prior to September 15, 2019      
Long-term debt      
Debt instrument redemption percentage 105.375%    
Debt instrument redemption percentage with payment of premium and interest 100.00%    
5.375% Senior Notes due 2024 | Prior to September 15, 2019 | Maximum      
Long-term debt      
Percent of aggregate principal amount that can be redeemed 35.00%    
5.375% Senior Notes due 2024 | On or after September 15, 2019      
Long-term debt      
Debt instrument redemption percentage 104.031%    
5.375% Senior Notes due 2024 | On or after September 15, 2022      
Long-term debt      
Debt instrument redemption percentage 100.00%