Regulatory Matters (Tables)

6 Months Ended

Jun. 30, 2021

Regulated Operations [Abstract]

Regulatory Assets and Liabilities [Table Text Block]

Regulatory Assets and Liabilities	June 30, 2021	December 31, 2020
Millions
Non-Current Regulatory Assets
Defined Benefit Pension and Other Postretirement Benefit Plans	$252.0	$259.7
Income Taxes	109.4	113.7
Cost Recovery Riders	63.2	54.0
Asset Retirement Obligations	31.4	31.6
Manufactured Gas Plant	6.0	8.8
Fuel Adjustment Clause	18.3	—
PPACA Income Tax Deferral	4.5	4.5
Boswell Units 1 and 2 Net Plant and Equipment	2.2	5.0
Other	4.9	3.6
Total Non-Current Regulatory Assets	$491.9	$480.9
Current Regulatory Liabilities (a)
Fuel Adjustment Clause	$3.7	$3.7
Transmission Formula Rates Refund	2.4	2.9
Other	0.1	1.0
Total Current Regulatory Liabilities	6.2	7.6
Non-Current Regulatory Liabilities
Income Taxes	364.5	375.3
Wholesale and Retail Contra AFUDC	85.1	86.6
Plant Removal Obligations	45.5	41.2
Defined Benefit Pension and Other Postretirement Benefit Plans	2.4	4.4
North Dakota Investment Tax Credits	12.4	12.0
Conservation Improvement Program	1.3	1.5
Other	3.7	3.8
Total Non-Current Regulatory Liabilities	514.9	524.8
Total Regulatory Liabilities	$521.1	$532.4

(a)Current regulatory liabilities are presented within Other Current Liabilities on the Consolidated Balance Sheet.