Annual report pursuant to Section 13 and 15(d)

SENIOR AND CONVERTIBLE SENIOR NOTES, NET - Narrative (Details)

v3.8.0.1
SENIOR AND CONVERTIBLE SENIOR NOTES, NET - Narrative (Details) - USD ($)
1 Months Ended 12 Months Ended
Jun. 30, 2017
Dec. 31, 2017
Sep. 30, 2017
Dec. 31, 2016
Jun. 30, 2015
Dec. 31, 2013
Mar. 31, 2013
Apr. 30, 2012
Dec. 31, 2010
Debt Instrument [Line Items]                  
Percentage of wholly owned subsidiary   100.00%              
Senior Notes [Member] | 7.15% senior notes due 2020 [Member]                  
Debt Instrument [Line Items]                  
Aggregate principal amount of offering                 $ 200,000,000
Debt instrument, stated rate   7.15%   7.15%         7.15%
Percent of debt instrument par value issued           106.699%     97.567%
Add-on to existing 7.50% senior notes           $ 100,000,000      
Effective percentage of debt instrument           5.875%     7.50%
Senior Notes [Member] | 7.00% senior notes due 2022 [Member]                  
Debt Instrument [Line Items]                  
Aggregate principal amount of offering               $ 300,000,000  
Debt instrument, stated rate   7.00%   7.00%       7.00%  
Senior Notes [Member] | 6.25% senior notes due 2015 [Member]                  
Debt Instrument [Line Items]                  
Debt instrument, stated rate               6.25%  
Aggregate principal amount repurchased               $ 285,000,000  
Senior Notes [Member] | 7.731% senior subordinated notes due 2017 [Member]                  
Debt Instrument [Line Items]                  
Debt instrument, stated rate             7.731% 7.731%  
Aggregate principal amount repurchased             $ 99,800,000 $ 26,100,000  
Senior Notes [Member] | 4.50% senior notes due 2018 [Member]                  
Debt Instrument [Line Items]                  
Aggregate principal amount of offering             $ 175,000,000    
Debt instrument, stated rate   4.50%   4.50%     4.50%    
Senior Notes [Member] | 6.00% senior notes due 2025 [Member]                  
Debt Instrument [Line Items]                  
Aggregate principal amount of offering         $ 200,000,000.0        
Debt instrument, stated rate   6.00%   6.00% 6.00%        
Senior Notes [Member] | 5.125% senior notes due 2027 [Member]                  
Debt Instrument [Line Items]                  
Aggregate principal amount of offering $ 300,000,000.0                
Debt instrument, stated rate 5.125% 5.125%              
Senior Notes [Member] | 1.875% convertible senior notes due 2032 [Member]                  
Debt Instrument [Line Items]                  
Debt instrument, stated rate   1.875%   1.875%          
Percentage of principal in the event of a repurchase 100.00%                
Aggregate principal amount repurchased     $ 126,500,000            
Loss on extinguishment of debt   $ 300,000              
Senior Notes [Member] | 1.875% convertible senior notes due 2032 [Member] | Privately negotiated transactions                  
Debt Instrument [Line Items]                  
Aggregate principal amount repurchased $ 51,900,000                
Senior Notes [Member] | 1.875% convertible senior notes due 2032 [Member] | Remaining redemptions                  
Debt Instrument [Line Items]                  
Aggregate principal amount repurchased $ 74,600,000