Operations and Significant Accounting Policies (Tables)

3 Months Ended

Mar. 31, 2016

Organization, Consolidation and Presentation of Financial Statements [Abstract]

Inventories [Table Text Block]

Inventories	March 31, 2016			December 31, 2015
Millions
Fuel (a)		$56.5			$58.1
Materials and Supplies	49.0			49.1
Raw Materials	2.6			2.7
Work in Progress	0.8			—
Finished Goods	7.4			7.5
Reserve for Obsolescence	(0.3		)	(0.3		)
Total Inventories		$116.0			$117.1

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

Prepayments and Other Current Assets [Table Text Block]

Prepayments and Other Current Assets	March 31, 2016		December 31, 2015
Millions
Deferred Fuel Adjustment Clause		$12.4		$10.6
Restricted Cash (a)	11.5		5.6
Other	17.6		19.5
Total Prepayments and Other Current Assets		$41.5		$35.7

(a) Restricted Cash includes collateral deposits required under ALLETE Clean Energy’s loan agreements and cash pledged as collateral for U.S. Water Services’ standby letters of credit.

Other Current Liabilities [Table Text Block]

Other Current Liabilities	March 31, 2016		December 31, 2015
Millions
Customer Deposits		$14.0		$15.1
Power Purchase Agreements	23.6		23.3
Other	45.2		47.7
Total Other Current Liabilities		$82.8		$86.1

Other Non-Current Liabilities [Table Text Block]

Other Non-Current Liabilities	March 31, 2016		December 31, 2015
Millions
Asset Retirement Obligation		$136.2		$131.4
Power Purchase Agreements	131.9		138.1
Contingent Consideration (a)	36.7		36.6
Other	42.3		42.9
Total Other Non-Current Liabilities		$347.1		$349.0

(a) Contingent Consideration relates to the estimated fair value of the earnings-based payment resulting from the U.S. Water Services acquisition. (See Note 3. Acquisitions and Note 5. Fair Value.)

Supplemental Statement of Cash Flows Information [Table Text Block]

Supplemental Statement of Cash Flows Information.

Three Months Ended March 31,	2016		2015
Millions
Cash Paid During the Period for Interest – Net of Amounts Capitalized		$19.6		$15.3
Cash Paid During the Period for Income Taxes		$0.1		$0.1
Noncash Investing and Financing Activities
Decrease in Accounts Payable for Capital Additions to Property, Plant and Equipment	$(25.6)		$(32.2)
Capitalized Asset Retirement Costs		$3.5		$1.2
AFUDC–Equity		$0.9		$0.9
Contingent Consideration	—			$35.7