Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (c)

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.14)

-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 14

-Article 5

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- Definition

The amount of expense recognized in the current period that reflects the allocation of the cost of tangible assets over the assets' useful lives. Includes production and non-production related depreciation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

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- Definition

Amount before accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

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-Section S99

-Paragraph 1

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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-Topic 210

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-Section S99

-Paragraph 1

-Subparagraph (SX 210.5-02.13)

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-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

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Property, Plant and Equipment (Details) (USD $)	3 Months Ended		9 Months Ended
Property, Plant and Equipment (Details) (USD $)	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2014	Dec. 31, 2013	Mar. 31, 2014
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	$ 2,112,118,000us-gaap_PropertyPlantAndEquipmentGross		$ 2,112,118,000us-gaap_PropertyPlantAndEquipmentGross		$ 2,001,019,000us-gaap_PropertyPlantAndEquipmentGross
Accumulated depreciation	1,534,995,000		1,534,995,000		1,469,052,000
Property, plant and equipment, net	577,123,000us-gaap_PropertyPlantAndEquipmentNet		577,123,000us-gaap_PropertyPlantAndEquipmentNet		531,967,000us-gaap_PropertyPlantAndEquipmentNet
Depreciation expense	24,700,000us-gaap_Depreciation	22,200,000us-gaap_Depreciation	72,300,000us-gaap_Depreciation	66,700,000us-gaap_Depreciation
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	55,624,000		55,624,000		55,624,000
Buildings and building improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	430,695,000		430,695,000		411,149,000
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	1,549,999,000		1,549,999,000		1,465,255,000
Projects in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	$ 75,800,000		$ 75,800,000		$ 68,991,000