Consolidated Statements of Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Total Amkor Stockholders' Equity	Common Stock	Additional Paid- In Capital	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Treasury Stock	Noncontrolling Interest in Subsidiaries
Balance at beginning of period, shares at Dec. 31, 2018			285,352
Balance at beginning of period, shares at Dec. 31, 2018							(45,967)
Balance at beginning of period at Dec. 31, 2018	$ 1,855,900	$ 1,830,540	$ 285	$ 1,909,425	$ 113,189	$ 23,812	$ (216,171)	$ 25,360
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	(22,668)	(22,879)			(22,879)			211
Other comprehensive income (loss)	(2,356)	(2,356)				(2,356)
Treasury stock acquired through surrender of shares for tax withholding, shares							(5)
Treasury stock acquired through surrender of shares for tax withholding	(48)	(48)					$ (48)
Issuance of stock through share-based compensation plans, shares			78
Issuance of stock through share-based compensation plans	286	286	$ 0	286
Share-based compensation	1,468	1,468		1,468
Balance at end of period, shares at Mar. 31, 2019			285,430
Balance at end of period, shares at Mar. 31, 2019							(45,972)
Balance at end of period at Mar. 31, 2019	$ 1,832,582	1,807,011	$ 285	1,911,179	90,310	21,456	$ (216,219)	25,571
Balance at beginning of period, shares at Dec. 31, 2019	286,877		286,877
Balance at beginning of period, shares at Dec. 31, 2019	(46,072)						(46,072)
Balance at beginning of period at Dec. 31, 2019	$ 1,990,239	1,963,739	$ 287	1,927,739	234,077	19,115	$ (217,479)	26,500
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income (loss)	64,497	63,889			63,889			608
Other comprehensive income (loss)	594	594				594
Treasury stock acquired through surrender of shares for tax withholding, shares							(5)
Treasury stock acquired through surrender of shares for tax withholding	(54)	(54)					$ (54)
Issuance of stock through share-based compensation plans, shares			216
Issuance of stock through share-based compensation plans	1,519	1,519		1,519
Share-based compensation	$ 1,830	1,830		1,830
Balance at end of period, shares at Mar. 31, 2020	287,093		287,093
Balance at end of period, shares at Mar. 31, 2020	(46,077)						(46,077)
Balance at end of period at Mar. 31, 2020	$ 2,058,625	$ 2,031,517	$ 287	$ 1,931,088	$ 297,966	$ 19,709	$ (217,533)	$ 27,108