Equity Method Investments (Narrative) (Details) $ in Millions |
12 Months Ended |
|---|---|
|
Dec. 31, 2015
USD ($)
| |
| Schedule of Equity Method Investments [Line Items] | |
| Utilities Operating Expense, Maintenance and Operations | $ 526.1 |
| Millennium Pipeline | |
| Schedule of Equity Method Investments [Line Items] | |
| Utilities Operating Expense, Maintenance and Operations | $ 13.1 |