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Commitments And Contingencies (Tables) | 9 Months Ended
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Sep. 30, 2017
Commitments and Contingencies [Line Items] |
Other Purchase Obligations | At September 30, 2017, minimum future commitments related to these purchase obligations were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Purchased power (a) |  | $1,278 |  |  |  | $1,194 |  |  |  | $84 |
Natural gas | 847 |  |  | 422 |  |  | 425 |
Coal (b) | 144 |  |  | 66 |  |  | 78 |
Other (c) | 34 |  |  | 25 |  |  | 1 |
|  | $2,303 |  |  |  | $1,707 |  |  |  | $588 |
(a) | Includes payments required by purchased power agreements for capacity rights and minimum quantities of MWhs required to be purchased.
(b) | Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2017 regarding expected future usage, which is subject to change.
(c) | Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2017.
MGP Site Estimated Future Costs And Recorded Liabilities | At September 30, 2017, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, were as follows (in millions). At September 30, 2017, such amounts for WPL were not material.
| Alliant Energy |  | IPL
Range of estimated future costs |  | $12 |  | - | $31 |  |  | $10 |  | - | $27
Current and non-current environmental liabilities | 16 |  | 14
IPL [Member] |
Commitments and Contingencies [Line Items] |
Other Purchase Obligations | At September 30, 2017, minimum future commitments related to these purchase obligations were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Purchased power (a) |  | $1,278 |  |  |  | $1,194 |  |  |  | $84 |
Natural gas | 847 |  |  | 422 |  |  | 425 |
Coal (b) | 144 |  |  | 66 |  |  | 78 |
Other (c) | 34 |  |  | 25 |  |  | 1 |
|  | $2,303 |  |  |  | $1,707 |  |  |  | $588 |
(a) | Includes payments required by purchased power agreements for capacity rights and minimum quantities of MWhs required to be purchased.
(b) | Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2017 regarding expected future usage, which is subject to change.
(c) | Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2017.
MGP Site Estimated Future Costs And Recorded Liabilities | At September 30, 2017, estimated future costs expected to be incurred for the investigation, remediation and monitoring of the MGP sites, as well as environmental liabilities recorded on the balance sheets for these sites, were as follows (in millions). At September 30, 2017, such amounts for WPL were not material.
| Alliant Energy |  | IPL
Range of estimated future costs |  | $12 |  | - | $31 |  |  | $10 |  | - | $27
Current and non-current environmental liabilities | 16 |  | 14
WPL [Member] |
Commitments and Contingencies [Line Items] |
Other Purchase Obligations | At September 30, 2017, minimum future commitments related to these purchase obligations were as follows (in millions):
| Alliant Energy |  | IPL |  | WPL
Purchased power (a) |  | $1,278 |  |  |  | $1,194 |  |  |  | $84 |
Natural gas | 847 |  |  | 422 |  |  | 425 |
Coal (b) | 144 |  |  | 66 |  |  | 78 |
Other (c) | 34 |  |  | 25 |  |  | 1 |
|  | $2,303 |  |  |  | $1,707 |  |  |  | $588 |
(a) | Includes payments required by purchased power agreements for capacity rights and minimum quantities of MWhs required to be purchased.
(b) | Corporate Services entered into system-wide coal contracts on behalf of IPL and WPL that include minimum future commitments. These commitments were assigned to IPL and WPL based on information available as of September 30, 2017 regarding expected future usage, which is subject to change.
(c) | Includes individual commitments incurred during the normal course of business that exceeded $1 million at September 30, 2017.

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- Definition Long-Term Purchase Commitment, Operating Expenses Purchase Obligation [Table Text Block] + References No definition available. + Details
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- Definition Tabular disclosure of material liabilities for remediation, site restoration, postclosure, monitoring commitments, or other exit costs that may occur on the sale, disposal or abandonment of a property as a result of unanticipated contamination of the assets. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section S99 -Paragraph 1 -Subparagraph (SAB Topic 5.Y.Q4) -URI http://asc.fasb.org/extlink&oid=27011672&loc=d3e149879-122751 + Details
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