Earnings Per Share Earnings Per Share (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended
Mar. 31, 2015	Mar. 31, 2014
Dilutive Securities Adjustments [Line Items]
Net income attributable to Amkor	$ 28,781us-gaap_NetIncomeLoss	$ 20,633us-gaap_NetIncomeLoss
Income allocated to participating securities	68	105
Net income available to Amkor common stockholders — basic	28,713	20,528
Adjustment for dilutive securities on net income:
Net income reallocated to participating securities	0	3
Net income attributable to Amkor — diluted	28,713	21,438
Weighted average shares outstanding — basic	236,708	216,757
Effect of dilutive securities:
Weighted average shares outstanding — diluted	237,424	235,497
Net income attributable to Amkor per common share:
Basic (in dollars per share)	$ 0.12us-gaap_EarningsPerShareBasic	$ 0.09us-gaap_EarningsPerShareBasic
Diluted (in dollars per share)	$ 0.12us-gaap_EarningsPerShareDiluted	$ 0.09us-gaap_EarningsPerShareDiluted
Convertible Senior Subordinated Notes Due April 2014 [Member]
Adjustment for dilutive securities on net income:
Interest on 6.0% convertible notes due 2014, net of tax	$ 0	$ 907
Effect of dilutive securities:
6.0% convertible notes due 2014	0	18,631
Net income attributable to Amkor per common share:
Debt Instrument, Interest Rate, Stated Percentage	6.00%
Stock Options Dilutive Effect [Member]
Effect of dilutive securities:
Stock options	716	109

Adjustment for dilutive securities on net income, net income reallocated to participating securities

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