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Accumulated Other Comprehensive Loss (Narrative) (Details) (Millennium Pipeline, USD $)
In Millions, unless otherwise specified |
3 Months Ended | |
|---|---|---|
|
Mar. 31, 2015
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Mar. 31, 2014
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|
Millennium Pipeline
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| Accumulated Other Comprehensive Loss [Line Items] | ||
| Other Comprehensive Income Unrecognized Gain Loss On Derivatives Arising During Period Net Of Tax | $ 26.4 | $ 16.6 |
| Debt Instrument, Maturity Date | Jun. 01, 2025 | |