The following table summarizes information on the convertible debt at December 31 (in thousands):
| 2013 | 2012 | |||||||
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Convertible Notes due 2028: |
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Principal amount of the liability component |
$ | — | $ | 12,500 | ||||
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Unamortized discount |
— | (609 | ) | |||||
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Net carrying amount |
$ | — | $ | 11,891 | ||||
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Convertible Notes due 2015: |
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Principal amount of the liability component |
$ | 345,000 | $ | 345,000 | ||||
|
Unamortized discount |
(26,356 | ) | (42,914 | ) | ||||
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Net carrying amount |
$ | 318,644 | $ | 302,086 | ||||
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Convertible Notes due 2019: |
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Principal amount of the liability component |
$ | 690,000 | $ | 690,000 | ||||
|
Unamortized discount |
(126,594 | ) | (146,768 | ) | ||||
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Net carrying amount |
$ | 563,406 | $ | 543,232 | ||||
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Total Convertible Senior Notes |
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|
Principal amount of the liability component |
$ | 1,035,000 | $ | 1,047,500 | ||||
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Unamortized discount |
(152,950 | ) | (190,291 | ) | ||||
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Net carrying amount |
$ | 882,050 | $ | 857,209 | ||||
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