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Property, Plant, and Equipment - Additional Information (Detail) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2018
Jun. 30, 2017
Jun. 30, 2018
Jun. 30, 2017
Depreciation expense $ 9.6 $ 8.4 $ 18.8 $ 16.9