Equity and Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended			9 Months Ended
	Sep. 30, 2016	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, Beginning balance		$ 1,217,536		$ 1,217,536	$ 1,129,449
Net income	$ 61,141		$ 28,582	66,102	64,046
Other comprehensive income	5,907	19,347	4,426	52,232	473
Issuance of stock through employee share-based compensation plans				2,600	657
Treasury stock acquired through surrender of shares for tax withholding				(446)	(548)
Share-based compensation expense				2,449	3,063
Subsidiary dividends paid to non-controlling interests				(413)	(123)
Equity, Ending balance	1,340,060		1,197,017	1,340,060	1,197,017
Amkor [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, Beginning balance		1,200,286		1,200,286	1,114,748
Net income				63,927	61,660
Other comprehensive income				52,232	473
Issuance of stock through employee share-based compensation plans				2,600	657
Treasury stock acquired through surrender of shares for tax withholding				(446)	(548)
Share-based compensation expense				2,449	3,063
Subsidiary dividends paid to non-controlling interests				0	0
Equity, Ending balance	1,321,048		1,180,053	1,321,048	1,180,053
Noncontrolling Interest [Member]
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Equity, Beginning balance		$ 17,250		17,250	14,701
Net income				2,175	2,386
Other comprehensive income				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 expense				0	0
Subsidiary dividends paid to non-controlling interests				(413)	(123)
Equity, Ending balance	$ 19,012		$ 16,964	$ 19,012	$ 16,964