Earnings Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Dilutive Securities Adjustments [Line Items]
Net income attributable to Amkor	$ 164,190	$ 51,098	$ 129,739
Income allocated to participating securities	0	(59)	(370)
Net income available to Amkor common stockholders — basic	164,190	51,039	129,369
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Net income reallocated to participating securities	0	0	6
Net income attributable to Amkor — diluted	$ 164,190	$ 51,039	$ 130,414
Weighted-average shares outstanding — basic	237,416	236,850	230,710
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Weighted-average shares outstanding — diluted	238,034	237,170	236,731
Earnings Per Share, Basic and Diluted [Abstract]
Basic	$ 0.69	$ 0.22	$ 0.56
Diluted	$ 0.69	$ 0.22	$ 0.55
Stock Options and Restricted Share Awards [Member]
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
Stock options and restricted share awards	618	320	712
Convertible Notes Due 2014 [Member]
Net Income (Loss) Available to Common Stockholders, Basic [Abstract]
Interest on 6.0% convertible notes due 2014, net of tax	$ 0	$ 0	$ 1,039
Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract]
6.0% convertible notes due 2014	0	0	5,309
Earnings Per Share, Basic and Diluted [Abstract]
Interest rate of convertible subordinated notes	6.00%	6.00%	6.00%