Summary of Significant Accounting Policies - Deferred Financing (Details) - USD ($) $ in Thousands  | 
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2017  | 
Dec. 31, 2016  | 
Dec. 31, 2015  | 
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| Changes in deferred financing costs | |||
| Balance at the beginning of the period | $ 4,033 | $ 2,337 | $ 2,485 | 
| Deferred financing costs capitalized on new debt | 2,320 | ||
| Amortization of deferred financing costs | (824) | (624) | (148) | 
| Balance at the end of the period | $ 3,209 | $ 4,033 | $ 2,337 | 
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- References No definition available. 
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- Definition Amount of amortization expense attributable to debt issuance costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition Amount, after accumulated amortization, of debt issuance costs classified as noncurrent. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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- Definition The cash outflow paid to third parties in connection with debt origination, which will be amortized over the remaining maturity period of the associated long-term debt. Reference 1: http://www.xbrl.org/2003/role/presentationRef 
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