Annual report pursuant to Section 13 and 15(d)

Long Term Debt (2025 Notes and 2021 Notes) (Details)

v3.8.0.1
Long Term Debt (2025 Notes and 2021 Notes) (Details) - USD ($)
$ in Thousands
12 Months Ended
Dec. 31, 2017
Dec. 31, 2016
Dec. 31, 2015
Apr. 30, 2017
Debt Instrument [Line Items]        
Loss on extinguishment of debt $ 649 $ 640 $ 27,700  
Senior Notes | 2025 Notes and 2021 Notes        
Debt Instrument [Line Items]        
Deferred debt fees       $ 1,900
Senior Notes | 2025 Notes | Maximum        
Debt Instrument [Line Items]        
Percentage of principal       101.00%
Senior Notes | 2025 Notes | Minimum        
Debt Instrument [Line Items]        
Percentage of principal       100.00%
Senior Notes | 2021 Notes | Maximum        
Debt Instrument [Line Items]        
Percentage of principal       101.00%
Senior Notes | 2021 Notes | Minimum        
Debt Instrument [Line Items]        
Percentage of principal       100.00%
Senior Notes | 2019 Notes        
Debt Instrument [Line Items]        
Loss on extinguishment of debt     $ 27,700