Common Stock Common Stock (Equity Securities Offering) (Details) - Piedmont Natural Gas [Member] shares in Millions	Jun. 30, 2016 $ / shares shares
Forward Contract Indexed to Issuer's Equity [Line Items]
Shares offered	10.6
Then Forward Price \| $ / shares	$ 69.84
Shares required to net settle	2.1

Then Forward Price determined by the Equity Forward agreements

No definition available.

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- Definition

The number of issuer's shares to which the forward contract is indexed.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 5
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=6445032&loc=d3e90205-114008

+ Details

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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.

+ References

No definition available.

+ Details

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- Definition

Number of shares as a settlement alternative for each freestanding forward contract.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 40
-Section 50
-Paragraph 5
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=6445032&loc=d3e90205-114008

+ Details

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Data Type:	xbrli:sharesItemType
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- Details

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