Equity and Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			$ 1,403,404	$ 1,217,536
Net income	$ 116,459	$ 5,366	107,315	4,961
Other comprehensive income (loss)	(815)	26,978	13,001	46,325
Issuance of stock through employee share-based compensation plans			2,365	60
Treasury stock acquired through surrender of shares for tax withholding			(1,378)	(238)
Share-based compensation			2,516	1,626
Subsidiary dividends paid to non-controlling interests			(270)	(270)
Ending balance	1,526,954	1,270,000	1,526,954	1,270,000
Amkor
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			1,383,588	1,200,286
Net income			105,501	3,838
Other comprehensive income (loss)			13,001	46,325
Issuance of stock through employee share-based compensation plans			2,365	60
Treasury stock acquired through surrender of shares for tax withholding			(1,378)	(238)
Share-based compensation			2,516	1,626
Subsidiary dividends paid to non-controlling interests			0	0
Ending balance	1,505,594	1,251,897	1,505,594	1,251,897
Noncontrolling Interest
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning balance			19,816	17,250
Net income			1,814	1,123
Other comprehensive income (loss)			0	0
Issuance of stock through employee share-based compensation plans			0	0
Treasury stock acquired through surrender of shares for tax withholding			0	0
Share-based compensation			0	0
Subsidiary dividends paid to non-controlling interests			(270)	(270)
Ending balance	$ 21,360	$ 18,103	$ 21,360	$ 18,103