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Summary of Significant Accounting Policies - Short-term Investments (Details) - Successor - USD ($) $ in Thousands | 9 Months Ended | 12 Months Ended
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Sep. 30, 2017 | Dec. 31, 2016
Schedule of Held-to-maturity Securities [Line Items] |  |
Short-term investments | $ 17,501 | $ 17,501
Treasury bills |  |
Schedule of Held-to-maturity Securities [Line Items] |  |
Short-term investments | $ 17,500 | $ 17,500
Maturity term for short-term investments | 6 months | 6 months

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- Definition Amount after other than temporary impairment (OTTI) accretion, of investments in debt securities classified as held-to-maturity, expected to be converted to cash, sold or exchanged within one year or the normal operating cycle. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=66010992&loc=d3e26626-111562 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 320 -SubTopic 10 -Section 25 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=65884222&loc=d3e22054-111558 + Details
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