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Regulatory Matters (Tables) | 6 Months Ended
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Jun. 30, 2018
Regulated Operations [Abstract] |
Regulatory Assets and Liabilities [Table Text Block] |
Regulatory Assets and Liabilities | June 30, 2018 |  |  | December 31, 2017 |
Millions |  |  |
Non-Current Regulatory Assets |  |  |
Defined Benefit Pension and Other Postretirement Benefit Plans |  | $216.7 |  |  |  | $220.3 |
Income Taxes | 109.3 |  |  | 112.8 |
Asset Retirement Obligations | 31.0 |  |  | 29.6 |
Manufactured Gas Plant | 8.0 |  |  | 8.1 |
PPACA Income Tax Deferral | 5.0 |  |  | 5.0 |
Conservation Improvement Program | — |  |  | 3.3 |
Other | 4.5 |  |  | 5.6 |
Total Non-Current Regulatory Assets |  | $374.5 |  |  |  | $384.7 |
Current Regulatory Liabilities (a) |  |  |
Provision for Interim Rate Refund (b) |  | $32.5 |  |  | — |
Provision for Tax Reform Refund (c) | 6.7 |  |  | — |
Total Current Regulatory Liabilities | 39.2 |  |  | — |
Non-Current Regulatory Liabilities |  |  |
Income Taxes | 401.4 |  |  |  | $411.2 |
Wholesale and Retail Contra AFUDC | 60.2 |  |  | 57.9 |
Plant Removal Obligations | 23.0 |  |  | 20.3 |
Cost Recovery Riders | 16.8 |  |  | 2.2 |
North Dakota Investment Tax Credits | 14.4 |  |  | 14.1 |
Provision for Interim Rate Refund (b) | — |  |  | 23.7 |
Other | 0.2 |  |  | 2.6 |
Total Non-Current Regulatory Liabilities | 516.0 |  |  | 532.0 |
Total Regulatory Liabilities |  | $555.2 |  |  |  | $532.0 |
(a) | Current regulatory liabilities are presented within Other Current Liabilities on the Consolidated Balance Sheet.
(b) | This amount is expected to be refunded to Minnesota Power’s regulated retail customers in the first quarter of 2019 and includes $16.7 million of discounts provided to EITE customers that will be offset against interim rate refunds as of June 30, 2018 ($8.6 million as of December 31, 2017). (See 2016 Minnesota General Rate Case and Energy-Intensive Trade‑Exposed Customer Rates.)
(c) | We have recorded the impact of income tax changes for Minnesota Power and SWL&P resulting from the TCJA in 2018 as regulatory liabilities and a reduction in revenue as the benefits are deferred pending the outcome of regulatory proceedings with the MPUC and PSCW. (See Tax Cuts and Jobs Act of 2017.)

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- Definition The entire disclosure for detailed information about regulatory assets and liabilities, including current and noncurrent assets created when regulatory agencies permit the deferral of costs to the balance sheet that would otherwise be required to appear on the company's income statement and would be charged against current expenses or revenues, as well as current and noncurrent liabilities created when regulatory agencies permit. + References No definition available. + Details
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