Long-Term Debt - Net Interest Expense (Details) - USD ($) $ in Thousands |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2016 |
Sep. 30, 2015 |
Sep. 30, 2016 |
Sep. 30, 2015 |
|
| Debt Disclosure [Abstract] | ||||
| Interest expense | $ 10,745 | $ 10,897 | $ 34,224 | $ 29,057 |
| Interest income | (833) | (470) | (1,713) | (1,577) |
| Capitalized interest | (3,069) | (1,714) | (7,504) | (9,462) |
| Net interest expense | $ 6,843 | $ 8,713 | $ 25,007 | $ 18,018 |