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, common stock (in shares) at Dec. 31, 2020			288,923
Balance at beginning of period at Dec. 31, 2020	$ 2,353,959	$ 2,325,699	$ 289	$ 1,953,378	$ 562,502	$ 27,270	$ (217,740)	$ 28,260
Balance at beginning of period, treasury stock (in shares) at Sep. 30, 2021							(46,151)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	428,324	426,469			426,469			1,855
Other comprehensive income (loss)	(11,334)	(11,334)				(11,334)
Treasury stock acquired through surrender of shares for tax withholding (in shares)							(57)
Treasury stock acquired through surrender of shares for tax withholding	(1,321)	(1,321)					$ (1,321)
Issuance of stock through share-based compensation plans (in shares)			1,418
Issuance of stock through share-based compensation plans	11,852	11,852	$ 1	11,851
Share-based compensation	7,978	7,978		7,978
Cash dividends declared	(29,330)	(29,330)			(29,330)
Subsidiary dividends to non-controlling interests	(449)							(449)
Balance at end of period, common stock (in shares) at Sep. 30, 2021			290,341
Balance at end of period at Sep. 30, 2021	2,759,679	2,730,013	$ 290	1,973,207	959,641	15,936	$ (219,061)	29,666
Balance at end of period, treasury stock (in shares) at Dec. 31, 2020							(46,094)
Balance at beginning of period, common stock (in shares) at Jun. 30, 2021			290,115
Balance at beginning of period at Jun. 30, 2021	2,583,070	2,554,248	$ 290	1,968,339	788,567	16,113	$ (219,061)	28,822
Balance at beginning of period, treasury stock (in shares) at Sep. 30, 2021							(46,151)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	181,847	180,854			180,854			993
Other comprehensive income (loss)	(177)	(177)				(177)
Issuance of stock through share-based compensation plans (in shares)			226
Issuance of stock through share-based compensation plans	1,828	1,828		1,828
Share-based compensation	3,040	3,040		3,040
Cash dividends declared	(9,780)	(9,780)			(9,780)
Subsidiary dividends to non-controlling interests	(149)							(149)
Balance at end of period, common stock (in shares) at Sep. 30, 2021			290,341
Balance at end of period at Sep. 30, 2021	$ 2,759,679	2,730,013	$ 290	1,973,207	959,641	15,936	$ (219,061)	29,666
Balance at end of period, treasury stock (in shares) at Jun. 30, 2021							(46,151)
Balance at beginning of period, common stock (in shares) at Dec. 31, 2021	244,315		290,466
Balance at beginning of period at Dec. 31, 2021	$ 2,972,546	2,942,276	$ 290	1,977,134	1,163,939	19,978	$ (219,065)	30,270
Balance at beginning of period, treasury stock (in shares) at Sep. 30, 2022	(46,155)						(46,155)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 603,154	601,522			601,522			1,632
Other comprehensive income (loss)	(33,561)	(33,561)				(33,561)
Treasury stock acquired through surrender of shares for tax withholding (in shares)							(4)
Treasury stock acquired through surrender of shares for tax withholding	(82)	(82)					$ (82)
Issuance of stock through share-based compensation plans (in shares)			500
Issuance of stock through share-based compensation plans	3,201	3,201	$ 1	3,200
Share-based compensation	10,711	10,711		10,711
Cash dividends declared	(36,721)	(36,721)			(36,721)
Subsidiary dividends to non-controlling interests	$ (405)							(405)
Balance at end of period, common stock (in shares) at Sep. 30, 2022	244,811		290,966
Balance at end of period at Sep. 30, 2022	$ 3,518,843	3,487,346	$ 291	1,991,045	1,728,740	(13,583)	$ (219,147)	31,497
Balance at end of period, treasury stock (in shares) at Dec. 31, 2021	(46,151)						(46,151)
Balance at beginning of period, common stock (in shares) at Jun. 30, 2022			290,788
Balance at beginning of period at Jun. 30, 2022	$ 3,227,550	3,196,295	$ 291	1,985,992	1,434,906	(5,747)	$ (219,147)	31,255
Balance at beginning of period, treasury stock (in shares) at Sep. 30, 2022	(46,155)						(46,155)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	$ 306,457	306,081			306,081			376
Other comprehensive income (loss)	(7,836)	(7,836)				(7,836)
Issuance of stock through share-based compensation plans (in shares)			178
Issuance of stock through share-based compensation plans	1,460	1,460		1,460
Share-based compensation	3,593	3,593		3,593
Cash dividends declared	(12,247)	(12,247)			(12,247)
Subsidiary dividends to non-controlling interests	$ (134)							(134)
Balance at end of period, common stock (in shares) at Sep. 30, 2022	244,811		290,966
Balance at end of period at Sep. 30, 2022	$ 3,518,843	$ 3,487,346	$ 291	$ 1,991,045	$ 1,728,740	$ (13,583)	$ (219,147)	$ 31,497
Balance at end of period, treasury stock (in shares) at Jun. 30, 2022							(46,155)