Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Statement of Comprehensive Income [Abstract]
Net income	$ 129,565	$ 267,705	$ 178,653
Other comprehensive income (loss), net of tax:
Adjustments to unrealized components of defined benefit pension plans	(3,644)	5,165	2,563
Foreign currency translation	4,937	11,092	5,783
Total other comprehensive income (loss)	1,293	16,257	8,346
Comprehensive income	130,858	283,962	186,999
Comprehensive income attributable to noncontrolling interests	(2,473)	(4,155)	(3,123)
Comprehensive income attributable to Amkor	$ 128,385	$ 279,807	$ 183,876