| Schedule of Maturities of Long-term Debt [Table Text Block] |
The following table summarizes the maturities of our borrowing obligations as of December 31, 2017 (dollars in thousands): | | | | | | | | | | | | | | Fiscal Year | | Convertible Debentures(1) | | Senior Notes | | Total | 2018 | | $ | — |
| | $ | — |
| | $ | — |
| 2019 | | — |
| | — |
| | — |
| 2020 | | — |
| | 450,000 |
| | 450,000 |
| 2021 | | — |
| | — |
| | — |
| 2022 | | 310,463 |
| | — |
| | 310,463 |
| Thereafter | | 1,026,488 |
| | 800,000 |
| | 1,826,488 |
| Total before unamortized discount | | 1,336,951 |
| | 1,250,000 |
| | 2,586,951 |
| Less: unamortized discount and issuance costs | | (277,455 | ) | | (9,902 | ) | | (287,357 | ) | Total long-term debt | | $ | 1,059,496 |
| | $ | 1,240,098 |
| | $ | 2,299,594 |
|
| | (1) | Pursuant to the terms of each convertible instrument, holders have the right to redeem the debt on specific dates prior to maturity. The repayment schedule above assumes that payment is due on the next redemption date after December 31, 2017. |
|
| Borrowing Obligations and Applicable Margin for Borrowings |
At December 31, 2017 and September 30, 2017, we had the following long-term borrowing obligations (dollars in thousands): | | | | | | | | | | December 31,
2017 | | September 30,
2017 | 5.625% Senior Notes due 2026, net of deferred issuance costs of $5.5 million and $5.7 million, respectively. Effective interest rate 5.625%. | $ | 494,453 |
| | $ | 494,298 |
| 5.375% Senior Notes due 2020, net of unamortized premium of $0.9 million and $1.0 million, respectively, and deferred issuance costs of $2.1 million and $2.3 million, respectively. Effective interest rate 5.375%. | 448,748 |
| | 448,630 |
| 6.000% Senior Notes due 2024, net of deferred issuance costs of $2.0 million and $2.1 million, respectively. Effective interest rate 6.000%. | 297,988 |
| | 297,910 |
| 1.00% Convertible Debentures due 2035, net of unamortized discount of $135.0 million and $140.9 million, respectively, and deferred issuance costs of $6.6 million and $6.9 million, respectively. Effective interest rate 5.622%. | 534,885 |
| | 528,690 |
| 2.75% Convertible Debentures due 2031, net of unamortized discount of $1.5 million and deferred issuance costs of $0.1 million as of September 30, 2017. Effective interest rate 7.432%. | 46,568 |
| | 376,121 |
| 1.25% Convertible Debentures due 2025, net of unamortized discount of $90.2 million and $92.7 million, respectively, and deferred issuance costs of $4.1 million and $4.3 million, respectively. Effective interest rate 5.578%. | 255,703 |
| | 253,054 |
| 1.50% Convertible Debentures due 2035, net of unamortized discount of $40.1 million and $42.5 million, respectively, and deferred issuance costs of $1.4 million and $1.5 million, respectively. Effective interest rate 5.394%. | 222,340 |
| | 219,875 |
| Deferred issuance costs related to our Revolving Credit Facility | (1,091 | ) | | (1,174 | ) | Total debt | 2,299,594 |
| | 2,617,404 |
| Less: current portion | — |
| | 376,121 |
| Total long-term debt | $ | 2,299,594 |
| | $ | 2,241,283 |
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