Quarterly report pursuant to Section 13 or 15(d)

SENIOR NOTES, NET - Schedule of Senior Notes, Net (Details)

v3.8.0.1
SENIOR NOTES, NET - Schedule of Senior Notes, Net (Details) - Senior Notes [Member] - USD ($)
Mar. 31, 2018
Dec. 31, 2017
Jun. 30, 2015
Debt Instrument [Line Items]      
Net debt issuance costs $ (12,576,000) $ (9,830,000)  
Senior notes, net 1,294,494,000 1,266,450,000  
4.50% senior notes due 2018 [Member]      
Debt Instrument [Line Items]      
Senior notes, gross $ 0 $ 175,000,000  
Stated interest rate 4.50% 4.50%  
7.15% senior notes due 2020 [Member]      
Debt Instrument [Line Items]      
Senior notes, gross $ 301,138,000 $ 301,280,000  
Stated interest rate 7.15% 7.15%  
Unamortized premium $ 1,138,000 $ 1,280,000  
7.00% senior notes due 2022 [Member]      
Debt Instrument [Line Items]      
Senior notes, gross $ 300,000,000 $ 300,000,000  
Stated interest rate 7.00% 7.00%  
6.00% senior notes due 2025 [Member]      
Debt Instrument [Line Items]      
Senior notes, gross $ 405,932,000 [1] $ 200,000,000 [1] $ 200,000,000
Stated interest rate 6.00% 6.00% 6.00%
Unamortized premium $ 5,932,000 $ 0  
5.125% senior notes due 2027 [Member]      
Debt Instrument [Line Items]      
Senior notes, gross $ 300,000,000 $ 300,000,000  
Stated interest rate 5.125% 5.125%  
[1] The $200.0 million 6.00% Senior Notes due 2025 outstanding at December 31, 2017 were issued at par and had no unamortized premium.