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Related Parties (Tables) | 9 Months Ended
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Sep. 30, 2018
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 nine months ended September 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Corporate Services billings |  | $43 |  |  |  | $48 |  |  |  | $128 |  |  |  | $130 |  |  |  | $33 |  |  |  | $37 |  |  |  | $100 |  |  |  | $100 |
Sales credited | 11 |  |  | 8 |  |  | 34 |  |  | 15 |  |  | 7 |  |  | 6 |  |  | 16 |  |  | 8 |
Purchases billed | 95 |  |  | 109 |  |  | 268 |  |  | 271 |  |  | 19 |  |  | 32 |  |  | 56 |  |  | 99 |
Net Intercompany Payables | Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| September 30, 2018 |  | December 31, 2017 |  | September 30, 2018 |  | December 31, 2017
Net payables to Corporate Services | $109 |  | $114 |  | $65 |  | $61
Related Amounts Billed Between Parties | The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):
| Three Months |  | Nine Months
| 2018 |  | 2017 |  | 2018 |  | 2017
ATC billings to WPL |  | $26 |  |  |  | $26 |  |  |  | $79 |  |  |  | $79 |
WPL billings to ATC | 3 |  |  | 2 |  |  | 8 |  |  | 8 |
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 nine months ended September 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Corporate Services billings |  | $43 |  |  |  | $48 |  |  |  | $128 |  |  |  | $130 |  |  |  | $33 |  |  |  | $37 |  |  |  | $100 |  |  |  | $100 |
Sales credited | 11 |  |  | 8 |  |  | 34 |  |  | 15 |  |  | 7 |  |  | 6 |  |  | 16 |  |  | 8 |
Purchases billed | 95 |  |  | 109 |  |  | 268 |  |  | 271 |  |  | 19 |  |  | 32 |  |  | 56 |  |  | 99 |
Net Intercompany Payables | Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| September 30, 2018 |  | December 31, 2017 |  | September 30, 2018 |  | December 31, 2017
Net payables to Corporate Services | $109 |  | $114 |  | $65 |  | $61
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 nine months ended September 30 were as follows (in millions):
| IPL |  | WPL
| Three Months |  | Nine Months |  | Three Months |  | Nine Months
| 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017 |  | 2018 |  | 2017
Corporate Services billings |  | $43 |  |  |  | $48 |  |  |  | $128 |  |  |  | $130 |  |  |  | $33 |  |  |  | $37 |  |  |  | $100 |  |  |  | $100 |
Sales credited | 11 |  |  | 8 |  |  | 34 |  |  | 15 |  |  | 7 |  |  | 6 |  |  | 16 |  |  | 8 |
Purchases billed | 95 |  |  | 109 |  |  | 268 |  |  | 271 |  |  | 19 |  |  | 32 |  |  | 56 |  |  | 99 |
Net Intercompany Payables | Net intercompany payables to Corporate Services were as follows (in millions):
| IPL |  | WPL
| September 30, 2018 |  | December 31, 2017 |  | September 30, 2018 |  | December 31, 2017
Net payables to Corporate Services | $109 |  | $114 |  | $65 |  | $61
Related Amounts Billed Between Parties | The related amounts billed between the parties for the three and nine months ended September 30 were as follows (in millions):
| Three Months |  | Nine Months
| 2018 |  | 2017 |  | 2018 |  | 2017
ATC billings to WPL |  | $26 |  |  |  | $26 |  |  |  | $79 |  |  |  | $79 |
WPL billings to ATC | 3 |  |  | 2 |  |  | 8 |  |  | 8 |

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