Operations and Significant Accounting Policies (Tables)

9 Months Ended

Sep. 30, 2017

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Inventories – Net [Table Text Block]

Inventories – Net	September 30, 2017			December 31, 2016
Millions
Fuel (a)		$39.6			$43.9
Materials and Supplies	48.2			48.7
Raw Materials	2.9			2.9
Work in Progress	3.5			1.0
Finished Goods	9.4			8.6
Reserve for Obsolescence	(1.0		)	(0.9		)
Total Inventories – Net		$102.6			$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	September 30, 2017		December 31, 2016
Millions
Deferred Fuel Adjustment Clause		$20.2		$18.6
Restricted Cash	6.5		2.2
Other	17.5		19.5
Total Prepayments and Other Current Assets		$44.2		$40.3

Other Non-Current Assets [Table Text Block]

Other Non-Current Assets	September 30, 2017		December 31, 2016
Millions
Contract Payment		$28.0		$29.6
Finance Receivable	11.0		11.5
Restricted Cash	8.6		8.6
Other	55.4		56.8
Total Other Non-Current Assets		$103.0		$106.5

Other Current Liabilities [Table Text Block]

Other Current Liabilities	September 30, 2017		December 31, 2016
Millions
PSAs		$24.8		$24.6
Other	59.9		49.1
Total Other Current Liabilities		$84.7		$73.7

Other Non-Current Liabilities [Table Text Block]

Other Non-Current Liabilities	September 30, 2017		December 31, 2016
Millions
Asset Retirement Obligation		$157.4		$136.6
PSAs	95.3		113.8
Contingent Consideration (a)	5.6		25.0
Other	42.8		47.3
Total Other Non-Current Liabilities		$301.1		$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.

Nine Months Ended September 30,	2017		2016
Millions
Cash Paid During the Period for Interest – Net of Amounts Capitalized		$51.4		$54.9
Cash Paid During the Period for Income Taxes		$0.4		$0.5
Noncash Investing and Financing Activities
Increase (Decrease) in Accounts Payable for Capital Additions to Property, Plant and Equipment	$1.2		$(19.5)
Capitalized Asset Retirement Costs		$19.7		$3.7
AFUDC–Equity		$0.7		$1.7
ALLETE Common Stock Contributed to the Pension Plans		$13.5	—
ALLETE Common Stock Received for Land Inventory	—			$8.0
Long-Term Finance Receivable for Land Inventory	—			$12.0