Annual report pursuant to Section 13 and 15(d)

Debt Instruments - Schedule of long-term debt (Details)

v3.6.0.2
Debt Instruments - Schedule of long-term debt (Details) - USD ($)
Dec. 31, 2016
Sep. 30, 2016
Dec. 31, 2015
Dec. 09, 2015
Debt Instrument [Line Items]        
Unamortized discount on long-term debt $ (92,753,000)   $ (110,423,000)  
Long-term debt, net 342,247,000   234,577,000  
Line of credit        
Debt Instrument [Line Items]        
Credit facility 90,000,000   0  
Interest rate (percent)   3.81%    
Convertible debt | 1.75% convertible senior notes due 2020        
Debt Instrument [Line Items]        
1.75% convertible senior notes due 2020 $ 345,000,000   $ 345,000,000  
Interest rate (percent) 1.75%     1.75%