Employee Incentive Plans - Summary of Weighted Average Inputs and Assumptions Used to Calculate Fair Value at Grant Date (Details) - TSR-Based Performance Shares - $ / shares	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Grant date fair value	$ 122.22	$ 151.98	$ 105.88
Grant date stock price	$ 95.13	$ 114.71	$ 91.22
Expected volatility of Kaiser Aluminum	49.37%	45.71%	27.40%
Expected volatility of peer companies	51.08%	50.69%	36.94%
Risk-free interest rate	1.59%	0.29%	0.58%
Dividend yield	3.24%	2.51%	2.96%