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Sale of NAC Subsidiary (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended	9 Months Ended
	Mar. 31, 2013	Sep. 30, 2013	Sep. 30, 2012	Mar. 15, 2013	Dec. 31, 2012
Discontinued Operation, Additional Disclosures [Abstract]
Goodwill		$ 0		$ 6.8	$ 6.8
Proceeds from sale of subsidiary		43.2	0
Gain on sale of subsidiary	35.6	35.6	0
Net assets and liabilities of subsidiary				5.5
Transaction costs for sale of subsidiary				$ 2.1

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Gain (loss) from sale or disposal of an organization or integrated set of activities (for example, but not limited to, a partnership or corporation) engaged in providing a product or service in a commercial, industrial, or professional environment.

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Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 350

-SubTopic 20

-Section 50

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The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

-URI http://asc.fasb.org/extlink&oid=6516133



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-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

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Net assets and liabilities of subsidiary

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Transaction costs for sale of subsidiary

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