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Debt (Narrative) (Details) - USD ($) $ in Millions	1 Months Ended
	Sep. 30, 2015	Aug. 31, 2015	Jun. 30, 2015
Debt [Line Items]
Commercial paper classified as long-term debt		$ 111.0
Senior Debentures [Member] | 3.3% senior debenture, due 2015 [Member]
Debt [Line Items]
Payments to retire long-term debt			$ 150.0
Interest rate			3.30%
Senior Debentures [Member] | 3.4% senior debenture, due 2025 [Member]
Debt [Line Items]
Interest rate		3.40%
Proceeds from issuance of long-term debt		$ 250.0
Pollution Control Revenue Bonds [Member] | 5.375% pollution control revenue bonds, due 2015 [Member]
Debt [Line Items]
Payments to retire long-term debt		$ 14.6
Interest rate		5.375%
Pollution Control Revenue Bonds [Member] | 5% pollution control revenue bonds, due 2015 [Member]
Debt [Line Items]
Payments to retire long-term debt	$ 16.0
Interest rate	5.00%

X

- Definition

Carrying value as of the balance sheet date of long-term unsecured obligations issued by corporations and other borrowers to investors (with maturities initially due after one year or beyond the operating cycle if longer), excluding current portion.

+ References

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



-Publisher FASB



-Name Accounting Standards Codification



-Topic 210



-SubTopic 10



-Section S99



-Paragraph 1



-Subparagraph (SX 210.5-02.22)



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



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



-Publisher SEC



-Name Regulation S-X (SX)



-Number 210



-Section 02



-Paragraph 22



-Article 5

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

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



-Publisher FASB



-Name Accounting Standards Codification



-Topic 210



-SubTopic 10



-Section S99



-Paragraph 1



-Subparagraph (SX 210.5-02.22(a)(1))



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



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



-Publisher SEC



-Name Regulation S-X (SX)



-Number 210



-Section 02



-Paragraph 22



-Article 5

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- Definition

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The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

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