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Related Parties (Narrative) (Details) - ATC LLC [Member] - Equity Method Investee [Member] - USD ($) $ in Millions | 3 Months Ended |  |
--- | --- | --- | ---
Jun. 30, 2020 | Sep. 30, 2020 | Dec. 31, 2019
WPL Owed ATC LLC [Member] |  |  |
Related Party Transactions [Line Items] |  |  |
Net amounts owed |  | $ 9 | $ 9
WPL [Member] |  |  |
Related Party Transactions [Line Items] |  |  |
Receipt of construction deposits | $ 46 |  |

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- Definition The cash inflow from borrowing by the entity from developers, builders, government agencies and municipalities for construction that are repaid in cash, generally on a straight-line basis over periods ranging from five to forty years. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3179-108585 + Details
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- Definition Receivables to be collected from (obligations owed to) related parties, net as of the balance sheet date where one party can exercise control or significant influence over another party; including affiliates, owners or officers and their immediate families, pension trusts, and so forth. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (d) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 235 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.4-08.(k)(1)) -URI http://asc.fasb.org/extlink&oid=26873400&loc=d3e23780-122690 + Details
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