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Inventories - Additional Information (Detail) $ in Millions | 3 Months Ended
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Jun. 30, 2018 USD ($)
Lower Of Cost Or Net Realizable Value Adjustment | $ 34.7
Lower Of Cost Or Net Realizable Value Adjustment Gross | 17.1
Airgas [Member] |
Lower Of Cost Or Net Realizable Value Adjustment Gross | $ 17.6

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