The carrying value of long-term debt outstanding, net of unamortized debt issuance costs, was as follows at September 30, 2016 and December 31, 2015: | | | | | | | | | | September 30, 2016 | | December 31, 2015 | | (in millions) | Senior notes: | | | | $500 million, 7.20% due June 15, 2018 | $ | 501 |
| | $ | 502 |
| $300 million, 6.30% due August 1, 2018 | 305 |
| | 307 |
| $400 million, 2.625% due October 1, 2019 | 398 |
| | 398 |
| $600 million, 3.15% due December 1, 2022 | 595 |
| | 595 |
| $600 million, 3.85% due October 1, 2024 | 595 |
| | 595 |
| $250 million, 8.15% due June 15, 2038 | 263 |
| | 263 |
| $400 million, 4.625% due December 1, 2042 | 396 |
| | 396 |
| $750 million, 4.95% due October 1, 2044 | 739 |
| | 738 |
| Total long-term debt | $ | 3,792 |
| | $ | 3,794 |
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