Quarterly report pursuant to Section 13 or 15(d)

Fair Value Disclosures (Details)

v3.3.0.814
Fair Value Disclosures (Details) - Senior Notes [Member] - USD ($)
Sep. 30, 2015
Jun. 02, 2015
Dec. 31, 2014
4.50% senior notes due 2018 [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 177,188,000   175,000,000
7.15% senior notes due 2020 [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 321,000,000   322,500,000
7.00% senior notes due 2022 [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 321,750,000   318,000,000
6.00% senior notes due 2025 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal   $ 200,000,000  
6.00% senior notes due 2025 [Member] | Level 2 [Member]      
Debt Instrument [Line Items]      
Aggregate Principal 200,000,000    
Fair value of fixed-rate debt      
Estimated Fair Value 201,000,000    
1.875% convertible senior notes due 2032 [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 $ 126,026,000   $ 124,444,000