Annual report pursuant to Section 13 and 15(d)

Long-Term Debt - Summary of Long-Term Debt (Details)

v3.8.0.1
Long-Term Debt - Summary of Long-Term Debt (Details) - USD ($)
$ in Thousands
Dec. 31, 2017
Oct. 11, 2017
Dec. 31, 2016
Dec. 21, 2016
Oct. 14, 2016
Apr. 21, 2015
Mar. 31, 2011
Debt Instrument [Line Items]              
Net unamortized original issue premium (discount) $ 0   $ 0        
Net unamortized debt issuance costs (34,781)   (27,174)        
Less: current maturities of long term debt (622)   (276)        
Debt reflected as long term 2,038,321   1,593,599        
Revolving credit agreement              
Debt Instrument [Line Items]              
Long-tern debt 0   0        
Building loans              
Debt Instrument [Line Items]              
Long-tern debt 0   0        
Stated interest rate             4.00%
Senior notes | 7.75% Senior Notes Due 2020              
Debt Instrument [Line Items]              
Long-tern debt $ 0   $ 0        
Stated interest rate 7.75%   7.75%        
Senior notes | 6.625% Senior Notes Due 2023              
Debt Instrument [Line Items]              
Long-tern debt $ 350,000   $ 350,000        
Net unamortized debt issuance costs $ (5,200)            
Stated interest rate 6.625%   6.625%     6.625%  
Senior notes | 6.000% Senior Notes Due 2024              
Debt Instrument [Line Items]              
Long-tern debt $ 650,000   $ 650,000        
Net unamortized debt issuance costs $ (9,900)            
Stated interest rate 6.00%   6.00%   6.00%    
Senior notes | 6.375% Senior Notes Due 2025              
Debt Instrument [Line Items]              
Long-tern debt $ 600,000   $ 600,000        
Net unamortized debt issuance costs $ (14,000)            
Stated interest rate 6.375%   6.375% 6.375%      
Senior notes | 6.375% Senior Notes Due 2026              
Debt Instrument [Line Items]              
Long-tern debt $ 450,000   $ 0        
Net unamortized debt issuance costs $ (5,500)            
Stated interest rate 6.375% 6.375%          
Construction loans              
Debt Instrument [Line Items]              
Long-tern debt $ 23,724   $ 21,049