Annual report pursuant to Section 13 and 15(d)

FAIR VALUE DISCLOSURES - Schedule of Fair Value of Fixed-Rate Debt (Details)

v3.3.1.900
FAIR VALUE DISCLOSURES - Schedule of Fair Value of Fixed-Rate Debt (Details) - Senior Notes [Member] - USD ($)
Dec. 31, 2015
Jun. 02, 2015
Dec. 31, 2014
Mar. 31, 2013
Sep. 30, 2012
Apr. 30, 2012
Dec. 31, 2010
4.50% senior notes [Member]              
Debt Instrument [Line Items]              
Aggregate Principal       $ 175,000,000      
Fair Value Disclosures (Textual) [Abstract]              
Debt instrument, stated rate 4.50%   4.50% 4.50%      
4.50% senior notes [Member] | Level 2 [Member]              
Debt Instrument [Line Items]              
Aggregate Principal $ 175,000,000   $ 175,000,000        
Fair value of fixed-rate debt              
Estimated Fair Value $ 175,000,000   $ 175,000,000        
7.15% senior notes [Member]              
Debt Instrument [Line Items]              
Aggregate Principal             $ 200,000,000
Fair Value Disclosures (Textual) [Abstract]              
Debt instrument, stated rate 7.15%   7.15%       7.15%
7.15% senior notes [Member] | Level 2 [Member]              
Debt Instrument [Line Items]              
Aggregate Principal $ 300,000,000   $ 300,000,000        
Fair value of fixed-rate debt              
Estimated Fair Value $ 315,750,000   $ 322,500,000        
7.00% senior notes [Member]              
Debt Instrument [Line Items]              
Aggregate Principal           $ 300,000,000  
Fair Value Disclosures (Textual) [Abstract]              
Debt instrument, stated rate 7.00%   7.00%     7.00%  
7.00% senior notes [Member] | Level 2 [Member]              
Debt Instrument [Line Items]              
Aggregate Principal $ 300,000,000   $ 300,000,000        
Fair value of fixed-rate debt              
Estimated Fair Value $ 313,500,000   $ 318,000,000        
6.00% senior notes [Member]              
Debt Instrument [Line Items]              
Aggregate Principal   $ 200,000,000.0          
Fair Value Disclosures (Textual) [Abstract]              
Debt instrument, stated rate 6.00% 6.00% 6.00%        
6.00% senior notes [Member] | Level 2 [Member]              
Debt Instrument [Line Items]              
Aggregate Principal $ 200,000,000            
Fair value of fixed-rate debt              
Estimated Fair Value $ 197,500,000            
1.875% convertible senior notes [Member]              
Debt Instrument [Line Items]              
Aggregate Principal         $ 126,500,000    
Fair Value Disclosures (Textual) [Abstract]              
Debt instrument, stated rate 1.875%   1.875%   1.875%    
1.875% convertible senior notes [Member] | Level 2 [Member]              
Debt Instrument [Line Items]              
Aggregate Principal $ 126,500,000   $ 126,500,000        
Fair value of fixed-rate debt              
Estimated Fair Value $ 124,128,000   $ 124,444,000