| Fair Value Measurements - Additional Information (Details) | Dec. 31, 2017  DerivativeInstrument | 
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| Fair Value Disclosures [Abstract] | |
| Number of open derivative financial instruments | 0 | 
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- Definition The number of derivative instruments of a particular group held by the entity. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef 
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| X | ||||||||||
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- References No definition available. 
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