Earnings Per Share - Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Earnings Per Share [Abstract]
Net income attributable to Amkor common stockholders, basic	$ 306,081	$ 180,854	$ 601,522	$ 426,469
Net income attributable to Amkor common stockholders, diluted	$ 306,081	$ 180,854	$ 601,522	$ 426,469
Weighted-average number of common shares outstanding - basic (in shares)	244,744	244,100	244,581	243,746
Effect of dilutive securities:
Share-based awards (in shares)	1,350	1,842	1,434	1,865
Weighted-average number of common shares outstanding - diluted (in shares)	246,094	245,942	246,015	245,611
Net income attributable to Amkor per common share:
Basic (in dollars per share)	$ 1.25	$ 0.74	$ 2.46	$ 1.75
Diluted (in dollars per share)	$ 1.24	$ 0.74	$ 2.45	$ 1.74