Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2015

Quarterly Financial Information Disclosure [Abstract]

Quarterly Financial Data (Unaudited) [Table Text Block]

Quarter Ended	Mar. 31		Jun. 30		Sept. 30		Dec. 31
Millions Except Earnings Per Share
2015
Operating Revenue		$320.0		$323.3		$462.5		$380.6
Operating Income		$56.4		$39.5		$85.2		$29.6
Net Income Attributable to ALLETE		$39.9		$22.5		$60.4		$18.3
Earnings Per Share of Common Stock
Basic		$0.85		$0.46		$1.24		$0.37
Diluted		$0.85		$0.46		$1.23		$0.37
2014
Operating Revenue		$296.5		$260.7		$288.9		$290.7
Operating Income		$48.3		$28.2		$60.8		$51.5
Net Income Attributable to ALLETE		$33.5		$16.8		$41.6		$32.9
Earnings Per Share of Common Stock
Basic		$0.81		$0.40		$0.97		$0.73
Diluted		$0.80		$0.40		$0.97		$0.73