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Property, Plant and Equipment (Details) (USD $)
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3 Months Ended | 6 Months Ended | |||
|---|---|---|---|---|---|
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Sep. 30, 2014
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Sep. 30, 2013
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Sep. 30, 2014
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Sep. 30, 2013
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Mar. 31, 2014
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| Property, Plant and Equipment [Line Items] | |||||
| Property, plant, and equipment costs | $ 2,100,780,000 | $ 2,100,780,000 | $ 2,001,019,000 | ||
| Accumulated depreciation | 1,515,678,000 | 1,515,678,000 | 1,469,052,000 | ||
| Property, plant and equipment, net | 585,102,000 | 585,102,000 | 531,967,000 | ||
| Depreciation expense | 24,300,000 | 23,000,000 | 47,600,000 | 44,400,000 | |
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Land [Member]
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| Property, Plant and Equipment [Line Items] | |||||
| Property, plant, and equipment costs | 69,895,000 | 69,895,000 | 55,624,000 | ||
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Buildings and building improvements [Member]
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| Property, Plant and Equipment [Line Items] | |||||
| Property, plant, and equipment costs | 418,525,000 | 418,525,000 | 411,149,000 | ||
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Machinery and equipment [Member]
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| Property, Plant and Equipment [Line Items] | |||||
| Property, plant, and equipment costs | 1,538,405,000 | 1,538,405,000 | 1,465,255,000 | ||
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Projects in progress [Member]
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| Property, Plant and Equipment [Line Items] | |||||
| Property, plant, and equipment costs | $ 73,955,000 | $ 73,955,000 | $ 68,991,000 | ||