Investments (Tables)

6 Months Ended

Jun. 30, 2015

Investments [Abstract]

Other Investments [Table Text Block]

Other Investments	June 30, 2015		December 31, 2014
Millions
ALLETE Properties		$88.6		$88.2
Available-for-sale Securities (a)	19.3		18.9
Cash Equivalents	2.8		2.9
Other	4.3		4.4
Total Other Investments		$115.0		$114.4

(a) As of June 30, 2015, the aggregate amount of available-for-sale corporate debt securities maturing in one year or less was $0.2 million, in one year to less than three years was $1.7 million, in three years to less than five years was $3.1 million, and in five or more years was $6.2 million.

Available-for-sale Securities [Table Text Block]

Available-For-Sale Securities
Millions		Gross Unrealized
	Cost	Gain	Loss	Fair Value
June 30, 2015	$19.8	$0.3	$0.8	$19.3
December 31, 2014	$19.6	$0.2	$0.9	$18.9
		Net	Gross Realized
		Proceeds	Gain	Loss
Quarter Ended June 30,
2015		$0.5	$0.1	—
2014		$2.1	$0.2	—
Six Months Ended June 30,
2015		$0.7	$0.1	—
2014		$2.7	$0.2	—