STATEMENTS OF CONSOLIDATED STOCKHOLDERS' EQUITY (UNAUDITED) - USD ($) $ in Millions		Total	Common Stock		Additional Paid in Capital	Retained Earnings	Treasury Stock	Accumulated Other Comprehensive Income (Loss)
Beginning balance at Dec. 31, 2020		$ 732.4	$ 0.2		$ 1,068.6	$ 158.2	$ (475.9)	$ (18.7)
Beginning balance (shares) at Dec. 31, 2020	[1]		15,812,169
Net income		4.5				4.5
Other comprehensive income, net of tax		9.1						9.1
Common shares issued (including impacts from Long-Term Incentive programs) (shares)	[1]		56,394
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(2.4)			(2.4)
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares (shares)	[1]		(20,625)
Cash dividends declared	[2]	(11.7)				(11.7)
Amortization of unearned equity compensation		3.1			3.1
Ending balance at Mar. 31, 2021		735.0	$ 0.2		1,069.3	151.0	(475.9)	(9.6)
Ending balance (shares) at Mar. 31, 2021	[1]		15,847,938
Beginning balance at Dec. 31, 2021		$ 692.5	$ 0.2		1,078.9	93.0	(475.9)	(3.7)
Beginning balance (shares) at Dec. 31, 2021		15,865,118	15,865,118	[3],[4]
Net income		$ 8.1				8.1
Other comprehensive income, net of tax		18.0						18.0
Common shares issued (including impacts from Long-Term Incentive programs) (shares)	[3],[4]		58,641
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares		(1.9)			(1.9)
Cancellation of shares to cover employees' tax withholdings upon vesting of non-vested shares (shares)	[3],[4]		(19,643)
Cash dividends declared	[5]	(12.5)				(12.5)
Amortization of unearned equity compensation		4.0			4.0
Ending balance at Mar. 31, 2022		$ 708.2	$ 0.2		$ 1,081.0	$ 88.6	$ (475.9)	$ 14.3
Ending balance (shares) at Mar. 31, 2022		15,904,116	15,904,116	[3],[4]

[1] There were no repurchases of common stock during the quarter ended March 31, 2021.

[2] Dividends declared per common share were $0.72 for the quarter ended March 31, 2021.

[3] At March 31, 2022, 593,072 shares were available for awards under the Kaiser Aluminum Corporation 2021 Equity and Incentive Compensation Plan (“2021 Plan”).

[4] There were no repurchases of common stock during the quarter ended March 31, 2022. At March 31, 2022, $93.1 million remained available to repurchase our common shares pursuant to the stock repurchase program.

[5] Dividends declared per common share were $0.77 for the quarter ended March 31, 2022.