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Related Parties (Tables) | 6 Months Ended
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Jun. 30, 2015
Related Party Transactions [Line Items] |
Services Provided, Sales Credited And Purchases | The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Six Months |  | Three Months |  | Six Months
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Corporate Services billings |  | $40 |  |  |  | $41 |  |  |  | $76 |  |  |  | $74 |  |  |  | $32 |  |  |  | $31 |  |  |  | $60 |  |  |  | $59 |
Sales credited | 2 |  |  | 2 |  |  | 6 |  |  | 4 |  |  | 6 |  |  | 3 |  |  | 12 |  |  | 2 |
Purchases billed | 89 |  |  | 108 |  |  | 168 |  |  | 207 |  |  | 19 |  |  | 28 |  |  | 33 |  |  | 58 |
Net Intercompany Payables | Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| June 30, 2015 |  | December 31, 2014 |  | June 30, 2015 |  | December 31, 2014
Net payables to Corporate Services | $95 |  | $84 |  | $49 |  | $58
Related Amounts Billed Between Parties | The related amounts billed between the parties for the three and six months ended June 30 were as follows (in millions):
| Three Months |  | Six Months
| 2015 |  | 2014 |  | 2015 |  | 2014
ATC billings to WPL |  | $25 |  |  |  | $24 |  |  |  | $50 |  |  |  | $48 |
WPL billings to ATC | 3 |  |  | 1 |  |  | 5 |  |  | 4 |
IPL [Member] |
Related Party Transactions [Line Items] |
Services Provided, Sales Credited And Purchases | The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Six Months |  | Three Months |  | Six Months
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Corporate Services billings |  | $40 |  |  |  | $41 |  |  |  | $76 |  |  |  | $74 |  |  |  | $32 |  |  |  | $31 |  |  |  | $60 |  |  |  | $59 |
Sales credited | 2 |  |  | 2 |  |  | 6 |  |  | 4 |  |  | 6 |  |  | 3 |  |  | 12 |  |  | 2 |
Purchases billed | 89 |  |  | 108 |  |  | 168 |  |  | 207 |  |  | 19 |  |  | 28 |  |  | 33 |  |  | 58 |
Net Intercompany Payables | Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| June 30, 2015 |  | December 31, 2014 |  | June 30, 2015 |  | December 31, 2014
Net payables to Corporate Services | $95 |  | $84 |  | $49 |  | $58
WPL [Member] |
Related Party Transactions [Line Items] |
Services Provided, Sales Credited And Purchases | The amounts billed for services provided, sales credited and purchases for the three and six months ended June 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Six Months |  | Three Months |  | Six Months
| 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014 |  | 2015 |  | 2014
Corporate Services billings |  | $40 |  |  |  | $41 |  |  |  | $76 |  |  |  | $74 |  |  |  | $32 |  |  |  | $31 |  |  |  | $60 |  |  |  | $59 |
Sales credited | 2 |  |  | 2 |  |  | 6 |  |  | 4 |  |  | 6 |  |  | 3 |  |  | 12 |  |  | 2 |
Purchases billed | 89 |  |  | 108 |  |  | 168 |  |  | 207 |  |  | 19 |  |  | 28 |  |  | 33 |  |  | 58 |
Net Intercompany Payables | Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| June 30, 2015 |  | December 31, 2014 |  | June 30, 2015 |  | December 31, 2014
Net payables to Corporate Services | $95 |  | $84 |  | $49 |  | $58
Related Amounts Billed Between Parties | The related amounts billed between the parties for the three and six months ended June 30 were as follows (in millions):
| Three Months |  | Six Months
| 2015 |  | 2014 |  | 2015 |  | 2014
ATC billings to WPL |  | $25 |  |  |  | $24 |  |  |  | $50 |  |  |  | $48 |
WPL billings to ATC | 3 |  |  | 1 |  |  | 5 |  |  | 4 |

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