Sale of Subsidiary to J-Devices (Details)	12 Months Ended			3 Months Ended	1 Months Ended		3 Months Ended
	Dec. 31, 2014 USD ($)	Dec. 31, 2013 USD ($)	Dec. 31, 2012 USD ($)	Jun. 30, 2014 J Devices [Member] USD ($)	Jun. 30, 2014 Amkor Iwate Company Ltd [Member] USD ($)	Jun. 30, 2014 Amkor Iwate Company Ltd [Member] JPY (¥)	Jun. 30, 2014 Amkor Iwate Company Ltd [Member] USD ($)	Dec. 31, 2014 Amkor Iwate Company Ltd [Member] USD ($)	Dec. 31, 2014 Amkor Iwate Company Ltd [Member] JPY (¥)	Sep. 30, 2014 Amkor Iwate Company Ltd [Member] USD ($)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Sale of Stock, Percentage of Ownership before Transaction					100.00%	100.00%
Significant Acquisitions and Disposals, Acquisition Costs or Sale Proceeds						¥ 1,100,000,000				$ 9,600,000
Proceeds from Divestiture of Interest in Consolidated Subsidiaries					1,000,000	100,000,000
Proceeds to Be Received from Divestiture of Interest in Consolidated Subsidiaries								8,600,000	1,000,000,000
Gain (Loss) on Disposition of Business	9,155,000	0	0				9,200,000
Disposal Group, Including Discontinued Operation, Foreign Currency Translation Gains (Losses)							12,600,000
Business Combination, Bargain Purchase, Gain Recognized, Amount				14,700,000
Proportionate Share Of Investee Bargain Purchase Gain				8,800,000
Combined Net Gain from Sale of Subsidiary							$ 18,000,000