Pension and Severance Plans (Defined Benefit Plans - Allocation of plan assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 155,211	$ 145,158	$ 123,370
Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,571	3,106
Treasury notes
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,069	3,516
Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,219	3,572
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,071	24,342
Mutual and commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	46,469	37,703
Mutual and commingled debt funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	30,988	26,680
Guaranteed investment contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34,281	33,931
Taiwan retirement fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12,748	11,359
Other, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(1,205)	949
Level 1
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	94,972	88,199
Level 1 | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,571	3,106
Level 1 | Treasury notes
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	8,069	3,516
Level 1 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,219	3,572
Level 1 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	16,071	24,342
Level 1 | Mutual and commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	38,939	30,801
Level 1 | Mutual and commingled debt funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	13,720	11,404
Level 1 | Guaranteed investment contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 1 | Taiwan retirement fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	12,748	11,359
Level 1 | Other, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	(2,365)	99
Level 2
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	60,239	56,959
Level 2 | Government bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Treasury notes
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Cash and cash equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Equity securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Mutual and commingled equity funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	7,530	6,902
Level 2 | Mutual and commingled debt funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	17,268	15,276
Level 2 | Guaranteed investment contracts
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	34,281	33,931
Level 2 | Taiwan retirement fund
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	0
Level 2 | Other, net
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 1,160	$ 850
Japan | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	65.00%
Japan | Equity funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	33.00%
Japan | Other, net
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	2.00%
Korea | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	15.00%
Korea | Equity funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	40.00%
Korea | Other, net
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	45.00%
Philippines | Debt securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	40.00%
Philippines | Equity funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	50.00%
Philippines | Other, net
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	10.00%