Earnings Per Share and Common Stock (Tables)

3 Months Ended

Mar. 31, 2022

Earnings Per Share [Abstract]

Reconciliation of Basic and Diluted Earnings Per Share [Table Text Block]

		2022			2021
Reconciliation of Basic and Diluted		Dilutive			Dilutive
Earnings Per Share	Basic	Securities	Diluted	Basic	Securities	Diluted
Millions Except Per Share Amounts
Three Months Ended March 31,
Net Income Attributable to ALLETE	$66.3		$66.3	$51.8		$51.8
Average Common Shares	53.3	—	53.3	52.1	0.1	52.2
Earnings Per Share	$1.24		$1.24	$0.99		$0.99