Quarterly Financial Data (Unaudited) (Tables)

12 Months Ended

Dec. 31, 2016

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
2016
Operating Revenue		$333.8		$314.8		$349.6		$341.5
Operating Income		$66.8		$42.2		$53.4		$61.1
Net Income Attributable to ALLETE		$45.9		$24.8		$40.3		$44.3
Earnings Per Share of Common Stock
Basic		$0.93		$0.50		$0.82		$0.89
Diluted		$0.93		$0.50		$0.81		$0.89
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