The cumulative amount of depreciation, depletion and amortization (related to property, plant and equipment, but not including land) that has been recognized in the income statement.

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

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-Publisher FASB

-Name Accounting Standards Codification

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-Section S99

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-Subparagraph (SX 210.5-02.14)

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-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 02

-Paragraph 14

-Article 5

Reference 5: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Principles Board Opinion (APB)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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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 Statement of Financial Accounting Standard (FAS)

-Number 95

-Paragraph 28

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 5

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

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- Definition

Gross amount, at the balance sheet date, of long-lived physical assets used in the normal conduct of business and not intended for resale. This can include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References

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

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 12

-Paragraph 5

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

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-Section 50

-Paragraph 1

-Subparagraph (b)

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-Topic 210

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-Paragraph 1

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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- Definition

Tangible assets that are held by an entity for use in the production or supply of goods and services, for rental to others, or for administrative purposes and that are expected to provide economic benefit for more than one year; net of accumulated depreciation. Examples include land, buildings, machinery and equipment, and other types of furniture and equipment including, but not limited to, office equipment, furniture and fixtures, and computer equipment and software.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 10

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-Paragraph 1

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-Publisher SEC

-Name Regulation S-X (SX)

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-Publisher SEC

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-Number 210

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 12

-Paragraph 5

-Subparagraph b, c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Property, Plant and Equipment (Details) (USD $)	3 Months Ended		6 Months Ended
Property, Plant and Equipment (Details) (USD $)	Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010	Mar. 31, 2011
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	$ 1,877,821,000		$ 1,877,821,000		$ 1,829,677,000
Accumulated depreciation	1,328,844,000		1,328,844,000		1,289,164,000
Property, plant and equipment, net	548,977,000		548,977,000		540,513,000
Depreciation expense	22,000,000	23,900,000	44,000,000	46,300,000
Land [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	46,529,000		46,529,000		46,497,000
Buildings and building improvements [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	381,258,000		381,258,000		375,611,000
Machinery and equipment [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	1,362,484,000		1,362,484,000		1,306,367,000
Projects in progress [Member]
Property, Plant and Equipment [Line Items]
Property, plant, and equipment costs	$ 87,550,000		$ 87,550,000		$ 101,202,000