Long-Term Debt - Convertible Senior Notes (Details)
2 Months Ended 3 Months Ended 6 Months Ended
May 05, 2015
$ / shares
Jun. 30, 2015
USD ($)
Jun. 30, 2016
USD ($)
Jun. 30, 2015
USD ($)
Jun. 30, 2016
USD ($)
Jun. 30, 2015
USD ($)
Carrying amount of Notes on the balance sheet:            
Interest expense     $ 3,524,166 $ 4,350,256 $ 7,027,561 $ 4,388,224
Senior convertible notes, including interest            
Debt Instrument [Line Items]            
Stated interest rate 2.50%          
Conversion ratio 25.5428          
Conversion price (in usd per share) | $ / shares $ 39.15          
Carrying amount of Notes on the balance sheet:            
Convertible senior notes, principal amount     230,000,000   230,000,000  
Unamortized debt discount     (24,998,630)   (24,998,630)  
Unamortized debt issuance costs     (4,944,207)   (4,944,207)  
Convertible senior notes, net     200,057,163   200,057,163  
Convertible senior notes, fair value     218,800,000   218,800,000  
Interest expense   $ 2,100,000     6,300,000  
Contractual coupon interest   1,000,000     2,900,000  
Debt discount amortization   900,000     2,800,000  
Debt issuance cost amortization   $ 200,000     $ 600,000  
Senior convertible notes, including interest | Level 2            
Debt Instrument [Line Items]            
Straight debt borrowing rate         5.75%  
Fair value of liability component     198,500,000   $ 198,500,000  
Fair value of equity component     $ 31,500,000   $ 31,500,000  
Effective interest rate     6.33%   6.33%  
Discount amortization period         5 years