Regulatory Matters (Tables)

6 Months Ended

Jun. 30, 2017

Regulated Operations [Abstract]

Regulatory Assets and Liabilities [Table Text Block]

Regulatory Assets and Liabilities	June 30, 2017		December 31, 2016
Millions
Current Regulatory Assets
Deferred Fuel Adjustment Clause		$16.7		$18.6
Total Current Regulatory Assets	16.7		18.6
Non-Current Regulatory Assets
Defined Benefit Pension and Other Postretirement Benefit Plans	223.4		226.1
Income Taxes (a)	35.0		33.8
Asset Retirement Obligations	28.4		26.0
Cost Recovery Riders	13.8		30.5
Conservation Improvement Program	7.1		4.0
PPACA Income Tax Deferral	5.0		5.0
Other	11.8		4.7
Total Non-Current Regulatory Assets	324.5		330.1
Total Regulatory Assets		$341.2		$348.7
Non-Current Regulatory Liabilities
Wholesale and Retail Contra AFUDC		$56.9		$56.8
North Dakota Investment Tax Credits	27.7		28.2
Plant Removal Obligations	19.0		19.1
Income Taxes	18.8		19.1
Other	3.4		2.6
Total Non-Current Regulatory Liabilities		$125.8		$125.8

(a) See Note 1. Operations and Significant Accounting Policies – Revision of Prior Balance Sheet.