Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Earnings Per Share [Abstract]
Net income available to Amkor common stockholders	$ 54,435	$ 60,089	$ 159,936	$ 63,927
Weighted-average number of common shares outstanding — basic	239,068	237,353	238,873	237,157
Effect of dilutive securities:
Stock options and restricted share awards (in shares)	572	839	737	429
Weighted-average number of common shares outstanding — diluted	239,640	238,192	239,610	237,586
Net income attributable to Amkor per common share:
Basic (in dollars per share)	$ 0.23	$ 0.25	$ 0.67	$ 0.27
Diluted (in dollars per share)	$ 0.23	$ 0.25	$ 0.67	$ 0.27