|
Goodwill Assets (Details) (USD $)
In Millions, unless otherwise specified |
Jun. 30, 2013
|
Mar. 31, 2013
|
Dec. 31, 2012
|
|---|---|---|---|
| Goodwill And Other Intangible Assets [Line Items] | |||
| Goodwill | $ 3,666.2 | $ 3,677.3 | |
| Disposal Group, Including Discontinued Operation, Goodwill | 11.0 | ||
|
Northern Indiana Gas Distribution [Member]
|
|||
| Goodwill And Other Intangible Assets [Line Items] | |||
| Goodwill | 17.8 | ||
| Disposal Group, Including Discontinued Operation, Goodwill | 1.0 | ||
|
Columbia Gas Transmission Operations [Member]
|
|||
| Goodwill And Other Intangible Assets [Line Items] | |||
| Goodwill | 2,000.0 | ||
|
Columbia Distribution [Member]
|
|||
| Goodwill And Other Intangible Assets [Line Items] | |||
| Goodwill | 1,700.0 | ||
| Disposal Group, Including Discontinued Operation, Goodwill | $ 10.0 |