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Income Taxes - Schedule of Non-Current Deferred Tax Assets and Liabilities Balance Sheet Captions (Detail) - USD ($) $ in Thousands | Dec. 31, 2017 | Dec. 31, 2016
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Income Tax Disclosure [Abstract] |  |
Other assets | $ 117 | $ 95
Deferred income taxes | $ 83,571 | $ 54,995

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