Significant Accounting Policies (Narrative) (Details) (Dominion Midstream Partners, LP, IPO)	1 Months Ended
Oct. 31, 2014
Dominion Midstream Partners, LP \| IPO
Subsidiary, Sale of Stock [Line Items]
Percentage of limited partner interests in Dominion Midstream Partners, LP	68.50%

Percentage of subsidiary's or equity investee's stock owned by parent company after stock transaction.

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration