Additional Cash Flow Information (Details) - USD ($) $ in Thousands |
9 Months Ended | |||
|---|---|---|---|---|
Sep. 30, 2018 |
Sep. 30, 2017 |
Dec. 31, 2017 |
Dec. 31, 2016 |
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| Supplemental Cash Flow Information [Abstract] | ||||
| Property, plant and equipment non-cash accruals | $ 3,529 | $ 0 | ||
| Accrued term loan issuance costs | 441 | 0 | ||
| Non-cash settlement of withholding taxes associated with the 2017 bonus accrual and vesting of certain awards | 5,733 | 828 | ||
| Non-cash settlement of the 2017 bonus accrual | 15,202 | 0 | ||
| Cash and cash equivalents | 172,317 | 138,023 | $ 128,273 | |
| Non-current restricted cash | 57,440 | 0 | 0 | |
| Total cash, cash equivalents and restricted cash shown in the statement of cash flows | $ 229,757 | $ 138,023 | $ 128,273 | $ 21,398 |
| X | ||||||||||
- Definition Noncash Settlement of Accrued Expense No definition available.
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| X | ||||||||||
- Definition Noncash Settlement of Accrued Expense, Taxes Withheld No definition available.
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| X | ||||||||||
- Definition Future cash outflow to pay for purchases of fixed assets that have occurred. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount of currency on hand as well as demand deposits with banks or financial institutions. Includes other kinds of accounts that have the general characteristics of demand deposits. Also includes short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Excludes cash and cash equivalents within disposal group and discontinued operation. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount of cash and cash equivalents, and cash and cash equivalents restricted to withdrawal or usage. Excludes amount for disposal group and discontinued operations. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Cash equivalents include, but are not limited to, short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition The amount of debt issuance costs that were incurred during a noncash or partial noncash transaction. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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| X | ||||||||||
- Definition Amount of cash restricted as to withdrawal or usage, classified as noncurrent. Cash includes, but is not limited to, currency on hand, demand deposits with banks or financial institutions, and other accounts with general characteristics of demand deposits. Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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| X | ||||||||||
- References No definition available.
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