Annual report pursuant to Section 13 and 15(d)

SENIOR AND CONVERTIBLE SENIOR NOTES - Narrative (Details)

v3.3.1.900
SENIOR AND CONVERTIBLE SENIOR NOTES - Narrative (Details) - USD ($)
1 Months Ended 12 Months Ended
Mar. 31, 2013
Sep. 30, 2012
Dec. 31, 2015
Dec. 31, 2014
Dec. 31, 2013
Jun. 02, 2015
Nov. 30, 2013
Mar. 13, 2013
Apr. 30, 2012
Dec. 31, 2010
Debt Instrument [Line Items]                    
Percentage of wholly owned subsidiary     100.00%              
Loss on early extinguishment of debt     $ 0 $ 0 $ (3,796,000)          
Senior Notes [Member] | 7.731% senior subordinated notes due 2017 [Member]                    
Debt Instrument [Line Items]                    
Loss on early extinguishment of debt $ 3,800,000                  
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] | 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 7.15% 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] | 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] | 1.875% convertible senior notes due 2032 [Member]                    
Debt Instrument [Line Items]                    
Aggregate principal amount of offering   $ 126,500,000                
Debt instrument, stated rate   1.875% 1.875% 1.875%            
Debt instrument, convertible, conversion ratio   0.0171985                
Debt instrument, convertible, conversion price   $ 58.14                
Debt instrument, convertible, conversion premium   47.50%                
Percentage of principal in the event of a repurchase   100.00%                
Senior Notes [Member] | 1.875% convertible senior notes due 2032 [Member] | Fifth anniversary [Member]                    
Debt Instrument [Line Items]                    
Debt instrument, convertible, conversion price   $ 58.14                
Senior Notes [Member] | 1.875% convertible senior notes due 2032 [Member] | Tenth anniversary [Member]                    
Debt Instrument [Line Items]                    
Debt instrument, convertible, conversion price   58.14                
Senior Notes [Member] | 1.875% convertible senior notes due 2032 [Member] | Fifteenth anniversary [Member]                    
Debt Instrument [Line Items]                    
Debt instrument, convertible, conversion price   $ 58.14                
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] | 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%