Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Dilutive Securities Adjustments [Line Items]
Net income attributable to Amkor	$ 60,089	$ 27,735	$ 63,927	$ 61,660
Income allocated to participating securities	0	0	0	(94)
Net income available to Amkor common stockholders	$ 60,089	$ 27,735	$ 63,927	$ 61,566
Adjustment for dilutive securities on net income:
Weighted average shares outstanding — basic	237,353	236,888	237,157	236,813
Effect of dilutive securities:
Stock options and restricted share awards	839	86	429	355
Weighted average shares outstanding — diluted	238,192	236,974	237,586	237,168
Net income attributable to Amkor per common share:
Basic (in dollars per share)	$ 0.25	$ 0.12	$ 0.27	$ 0.26
Diluted (in dollars per share)	$ 0.25	$ 0.12	$ 0.27	$ 0.26