Long-Term Debt - Convertible Senior Notes (Details) - USD ($)
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3 Months Ended |
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May 05, 2015 |
Mar. 31, 2017 |
Mar. 31, 2016 |
Dec. 31, 2016 |
| Carrying amount of Notes on the balance sheet: |
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| Interest expense |
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$ 3,624,136
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$ 3,503,395
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| Senior convertible notes, including interest |
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| Debt Instrument [Line Items] |
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| Stated interest rate |
2.50%
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| Conversion ratio |
25.5428
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| Conversion price (in usd per share) |
$ 39.15
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| Carrying amount of Notes on the balance sheet: |
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| Convertible senior notes, principal amount |
$ 230,000,000
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230,000,000
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$ 230,000,000
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| Unamortized debt discount |
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(20,571,894)
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(22,070,838)
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| Unamortized debt issuance costs |
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(4,068,692)
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(4,365,151)
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| Convertible senior notes, net |
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205,359,414
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$ 203,564,011
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| Convertible senior notes, fair value |
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218,700,000
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| Interest expense |
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3,200,000
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3,100,000
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| Contractual coupon interest |
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1,400,000
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1,400,000
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| Debt discount amortization |
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1,500,000
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1,400,000
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| Amortization of debt issuance costs |
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$ 300,000
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$ 300,000
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| Senior convertible notes, including interest | Level 2 |
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| Debt Instrument [Line Items] |
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| Straight debt borrowing rate |
5.75%
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| Fair value of liability component |
$ 198,500,000
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| Fair value of equity component |
$ 31,500,000
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| Discount amortization period |
5 years
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| Effective interest rate |
6.33%
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