Earnings Per Share - Calculation of EPS (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Earnings Per Share [Abstract]
Net income attributable to Amkor common stockholders, basic	$ 124,778	$ 125,806	$ 295,441	$ 245,615
Net income attributable to Amkor common stockholders, diluted	$ 124,778	$ 125,806	$ 295,441	$ 245,615
Weighted-average number of common shares outstanding - basic (in shares)	244,592	243,863	244,498	243,566
Effect of dilutive securities:
Share-based awards (in shares)	1,263	1,688	1,440	1,806
Weighted-average number of common shares outstanding - diluted (in shares)	245,855	245,551	245,938	245,372
Net income attributable to Amkor per common share:
Basic (in dollars per share)	$ 0.51	$ 0.52	$ 1.21	$ 1.01
Diluted (in dollars per share)	$ 0.51	$ 0.51	$ 1.20	$ 1.00