|
Related Parties (Sales Credited And Purchases Billed) (Details) (USD $)
In Millions, unless otherwise specified |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2012
|
Dec. 31, 2011
|
Dec. 31, 2010
|
|
|
Sales Credited [Member] | IPL [Member]
|
|||
| Related Party Transaction [Line Items] | |||
| Amounts billed between related parties | $ 10 | $ 31 | $ 28 |
|
Sales Credited [Member] | WPL [Member]
|
|||
| Related Party Transaction [Line Items] | |||
| Amounts billed between related parties | 14 | 28 | 24 |
|
Purchases Billed [Member] | IPL [Member]
|
|||
| Related Party Transaction [Line Items] | |||
| Amounts billed between related parties | 301 | 307 | 341 |
|
Purchases Billed [Member] | WPL [Member]
|
|||
| Related Party Transaction [Line Items] | |||
| Amounts billed between related parties | $ 61 | $ 77 | $ 73 |