Long-Term Debt (Tables)
 6 Months Ended
Jun. 30, 2017
Debt Disclosure [Abstract]  
Schedule of convertible senior notes
As of June 30, 2017 and December 31, 2016, the carrying amounts of the Notes on the consolidated balance sheets were calculated as follows:
 
June 30, 2017
 
December 31, 2016
Convertible senior notes, principal amount
$
230,000,000

 
$
230,000,000

Unamortized debt discount
(19,049,090
)
 
(22,070,838
)
Unamortized debt issuance costs
(3,767,512
)
 
(4,365,151
)
Convertible senior notes, net
$
207,183,398

 
$
203,564,011
Schedule of maturities of convertible senior notes
The undiscounted interest and principal payments due in relation to the Notes from June 30, 2017 to the maturity of the Notes on May 1, 2020 are as follows:
 
Total
2017
2018
2019
2020
Senior convertible notes, including interest
$
247,250,000

2,875,000

5,750,000

5,750,000

$
232,875,000