Operations and Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Inventories [Table Text Block]

Inventories – Net	June 30, 2017			December 31, 2016
Millions
Fuel (a)		$45.0			$43.9
Materials and Supplies	48.0			48.7
Raw Materials	2.8			2.9
Work in Progress	0.3			1.0
Finished Goods	8.3			8.6
Reserve for Obsolescence	(1.0		)	(0.9		)
Total Inventories – Net		$103.4			$104.2

(a) Fuel consists primarily of coal inventory at Minnesota Power.

Prepayments and Other Current Assets [Table Text Block]

Prepayments and Other Current Assets	June 30, 2017		December 31, 2016
Millions
Deferred Fuel Adjustment Clause		$16.7		$18.6
Restricted Cash	3.7		2.2
Other	18.4		19.5
Total Prepayments and Other Current Assets		$38.8		$40.3

Other Non-Current Assets [Table Text Block]

Other Non-Current Assets	June 30, 2017		December 31, 2016
Millions
Contract Payment		$28.4		$29.6
Finance Receivable	11.5		11.5
Restricted Cash	8.6		8.6
Other	56.3		56.8
Total Other Non-Current Assets		$104.8		$106.5

Other Current Liabilities [Table Text Block]

Other Current Liabilities	June 30, 2017		December 31, 2016
Millions
PSAs		$24.7		$24.6
Other	45.4		49.1
Total Other Current Liabilities		$70.1		$73.7

Other Non-Current Liabilities	June 30, 2017		December 31, 2016
Millions
Asset Retirement Obligation		$158.2		$136.6
PSAs	101.5		113.8
Contingent Consideration (a)	5.5		25.0
Other	43.9		47.3
Total Other Non-Current Liabilities		$309.1		$322.7

Other Non-Current Liabilities [Table Text Block]

Other Non-Current Liabilities	June 30, 2017		December 31, 2016
Millions
Asset Retirement Obligation		$158.2		$136.6
PSAs	101.5		113.8
Contingent Consideration (a)	5.5		25.0
Other	43.9		47.3
Total Other Non-Current Liabilities		$309.1		$322.7

(a) Contingent Consideration relates to the estimated fair value of the earnings-based payment resulting from the U.S. Water Services acquisition. (See Note 5. Fair Value.)

Supplemental Statement of Cash Flows Information [Table Text Block]

Supplemental Statement of Cash Flows Information.

Six Months Ended June 30,	2017		2016
Millions
Cash Paid During the Period for Interest – Net of Amounts Capitalized		$32.5		$32.9
Cash Paid During the Period for Income Taxes		$0.3		$0.4
Noncash Investing and Financing Activities
Decrease in Accounts Payable for Capital Additions to Property, Plant and Equipment	$(0.4)		$(24.4)
Capitalized Asset Retirement Costs		$19.7		$2.3
AFUDC–Equity		$0.4		$1.2
ALLETE Common Stock Contributed to the Pension Plans		$13.5	—