Business Segments (Tables)

9 Months Ended

Sep. 30, 2017

Segment Reporting [Abstract]

Business Segments [Table Text Block]

	Quarter Ended					Nine Months Ended
	September 30,					September 30,
	2017		2016			2017		2016
Millions
Operating Revenue
Regulated Operations	$277.6		$253.3			$824.1		$740.5
Energy Infrastructure and Related Services
ALLETE Clean Energy	13.5		14.7			56.8		57.1
U.S. Water Services	40.2		37.8			110.7		104.5
Corporate and Other	31.2		43.8			89.8		96.1
Total Operating Revenue		$362.5		$349.6			$1,081.4		$998.2
Net Income (Loss) Attributable to ALLETE
Regulated Operations		$34.2		$45.0			$110.1		$110.0
Energy Infrastructure and Related Services
ALLETE Clean Energy	0.6		1.0			11.1		9.7
U.S. Water Services	1.3		1.5			1.6		2.0
Corporate and Other	8.8		(7.2		)	8.0		(10.7		)
Total Net Income Attributable to ALLETE		$44.9		$40.3			$130.8		$111.0

	September 30, 2017		December 31, 2016
Millions
Assets
Regulated Operations	$3,811.7		$3,823.9
Energy Infrastructure and Related Services
ALLETE Clean Energy	560.3		566.0
U.S. Water Services	293.3		264.1
Corporate and Other	313.2		222.9
Total Assets		$4,978.5		$4,876.9