|
Equity Method Investments (Narrative) (Details) (USD $)
In Millions, unless otherwise specified |
1 Months Ended | 3 Months Ended | |
|---|---|---|---|
|
Feb. 11, 2015
|
Mar. 31, 2015
|
Mar. 31, 2014
|
|
| Schedule of Equity Method Investments [Line Items] | |||
| Contributions | $ 1,217.3 | ||
| Millennium Pipeline | |||
| Schedule of Equity Method Investments [Line Items] | |||
| Contributions | 0 | 2.6 | |
| Distributions | 16.6 | 7.1 | |
| Hardy Storage [Member] | |||
| Schedule of Equity Method Investments [Line Items] | |||
| Contributions | 0 | ||
| Distributions | 0.5 | 0.5 | |
| Pennant [Member] | |||
| Schedule of Equity Method Investments [Line Items] | |||
| Contributions | 0 | 28.4 | |
| Distributions | 1.2 | 0 | |
| Proceeds from Equity Method Investment, Dividends or Distributions, Return of Capital | $ 1.3 | ||