Earnings Per Share and Common Stock (Tables)

6 Months Ended

Jun. 30, 2021

Earnings Per Share [Abstract]

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

		2021			2020
Reconciliation of Basic and Diluted		Dilutive			Dilutive
Earnings Per Share	Basic	Securities	Diluted	Basic	Securities	Diluted
Millions Except Per Share Amounts
Quarter ended June 30,
Net Income Attributable to ALLETE	$27.9		$27.9	$20.1		$20.1
Average Common Shares	52.2	0.1	52.3	51.8	0.1	51.9
Earnings Per Share	$0.53		$0.53	$0.39		$0.39
Six Months Ended June 30,
Net Income Attributable to ALLETE	$79.7		$79.7	$86.4		$86.4
Average Common Shares	52.2	—	52.2	51.8	—	51.8
Earnings Per Share	$1.53		$1.53	$1.67		$1.67