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Related Parties (Tables) | 12 Months Ended
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Dec. 31, 2018
Related Party Transaction [Line Items] |
Services Provided, Sales Credited And Purchases Billed | The amounts billed for services provided, sales credited and purchases were as follows (in millions):
| IPL |  | WPL
| 2018 |  | 2017 |  | 2016 |  | 2018 |  | 2017 |  | 2016
Corporate Services billings |  | $170 |  |  |  | $177 |  |  |  | $161 |  |  |  | $132 |  |  |  | $135 |  |  |  | $133 |
Sales credited | 48 |  |  | 23 |  | 8 |  | 28 |  |  | 13 |  | 7
Purchases billed | 358 |  |  | 364 |  | 433 |  | 81 |  |  | 115 |  | 102
Net Intercompany Payables | As of December 31, net intercompany payables to Corporate Services were as follows (in millions):
| 2018 |  | 2017
IPL |  | $95 |  |  |  | $114 |
WPL | 71 |  |  | 61 |
Related Amounts Billed Between Parties | The related amounts billed between the parties were as follows (in millions):
| 2018 |  | 2017 |  | 2016
ATC billings to WPL |  | $106 |  |  |  | $105 |  |  |  | $110 |
WPL billings to ATC | 11 |  |  | 10 |  |  | 13 |
IPL [Member] |
Related Party Transaction [Line Items] |
Services Provided, Sales Credited And Purchases Billed | The amounts billed for services provided, sales credited and purchases were as follows (in millions):
| IPL |  | WPL
| 2018 |  | 2017 |  | 2016 |  | 2018 |  | 2017 |  | 2016
Corporate Services billings |  | $170 |  |  |  | $177 |  |  |  | $161 |  |  |  | $132 |  |  |  | $135 |  |  |  | $133 |
Sales credited | 48 |  |  | 23 |  | 8 |  | 28 |  |  | 13 |  | 7
Purchases billed | 358 |  |  | 364 |  | 433 |  | 81 |  |  | 115 |  | 102
Net Intercompany Payables | As of December 31, net intercompany payables to Corporate Services were as follows (in millions):
| 2018 |  | 2017
IPL |  | $95 |  |  |  | $114 |
WPL | 71 |  |  | 61 |
WPL [Member] |
Related Party Transaction [Line Items] |
Services Provided, Sales Credited And Purchases Billed | The amounts billed for services provided, sales credited and purchases were as follows (in millions):
| IPL |  | WPL
| 2018 |  | 2017 |  | 2016 |  | 2018 |  | 2017 |  | 2016
Corporate Services billings |  | $170 |  |  |  | $177 |  |  |  | $161 |  |  |  | $132 |  |  |  | $135 |  |  |  | $133 |
Sales credited | 48 |  |  | 23 |  | 8 |  | 28 |  |  | 13 |  | 7
Purchases billed | 358 |  |  | 364 |  | 433 |  | 81 |  |  | 115 |  | 102
Net Intercompany Payables | As of December 31, net intercompany payables to Corporate Services were as follows (in millions):
| 2018 |  | 2017
IPL |  | $95 |  |  |  | $114 |
WPL | 71 |  |  | 61 |
Related Amounts Billed Between Parties | The related amounts billed between the parties were as follows (in millions):
| 2018 |  | 2017 |  | 2016
ATC billings to WPL |  | $106 |  |  |  | $105 |  |  |  | $110 |
WPL billings to ATC | 11 |  |  | 10 |  |  | 13 |

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