| Schedule of Long-term Debt Instruments [Table Text Block] |
The following table reflects the carrying value of the Company's convertible debt as of June 30, 2015 and December 31, 2014 (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | June 30, 2015 | | December 31, 2014 | | 2016 Notes | | 2020 Notes | | Total | | 2016 Notes | | 2020 Notes | | Total | Principal | $ | 230,000 |
| | $ | 316,000 |
| | $ | 546,000 |
| | $ | 230,000 |
| | $ | — |
| | $ | 230,000 |
| Less: | | | | | | | | | | | | Unamortized interest discount | (7,415 | ) | | (55,899 | ) | | (63,314 | ) | | (12,165 | ) | | — |
| | (12,165 | ) | Deferred financing costs | (978 | ) | | (6,508 | ) | | (7,486 | ) | | (1,629 | ) | | — |
| | (1,629 | ) | Net carrying amount of Notes | $ | 221,607 |
| | $ | 253,593 |
| | $ | 475,200 |
| | $ | 216,206 |
| | $ | — |
| | $ | 216,206 |
|
The following table presents the amount of interest cost recognized for the three and six months ended June 30, 2015 and June 30, 2014 relating to the contractual interest coupon, accretion of the debt discount, and the amortization of financing costs (in thousands): | | | | | | | | | | | | | | | | | | | | | | | | | | For the Three Months Ended June 30, | | 2015 |
| 2014 | | 2016 Notes | | 2020 Notes | | Total | | 2016 Notes | | 2020 Notes | | Total | Contractual coupon interest | $ | 1,438 |
| | $ | 1,053 |
| | $ | 2,491 |
| | $ | 1,438 |
| | $ | — |
| | $ | 1,438 |
| Accretion of debt discount | 2,416 |
| | 2,569 |
| | 4,985 |
| | 2,255 |
| | — |
| | 2,255 |
| Amortization of deferred financing costs | 326 |
| | 349 |
| | 675 |
| | 326 |
| | — |
| | 326 |
| Total | $ | 4,180 |
| | $ | 3,971 |
| | $ | 8,151 |
| | $ | 4,019 |
| | $ | — |
| | $ | 4,019 |
|
| | | | | | | | | | | | | | | | | | | | | | | | | | | For the Six Months Ended June 30, | | 2015 | | 2014 | | 2016 Notes | | 2020 Notes | | Total | | 2016 Notes | | 2020 Notes | | Total | Contractual coupon interest | $ | 2,875 |
| | $ | 1,448 |
| | $ | 4,323 |
| | $ | 2,876 |
| | $ | — |
| | $ | 2,876 |
| Accretion of debt discount | 4,750 |
| | 3,434 |
| | 8,184 |
| | 4,434 |
| | — |
| — |
| 4,434 |
| Amortization of deferred financing costs | 652 |
| | 465 |
| | 1,117 |
| | 652 |
| | — |
| — |
| 652 |
| Total | $ | 8,277 |
| | $ | 5,347 |
| | $ | 13,624 |
| | $ | 7,962 |
| | $ | — |
| | $ | 7,962 |
|
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