Pension and Severance Plans (Defined Benefit Plans - Allocation of plan assets) (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 123,370	$ 115,725	$ 91,471
Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	50,467	55,873
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	36,479	33,699
Level 1 | Cash and Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	6,640	1,098
Level 1 | US Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	15,069	16,854
Level 1 | Foreign Securities
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10,162	16,826
Level 1 | Foreign Mutual Funds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	25,236	22,193
Level 1 | US Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	2,188
Level 1 | U.S. Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	0	2,144
Level 1 | Foreign Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	4,427	5,211
Level 1 | Foreign Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	5,713	520
Level 1 | Foreign Treasury Notes [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	2,587	4,686
Level 1 | Foreign Mutual Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	11,188	8,787
Level 1 | Taiwan Retirement Fund [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	10,451	10,094
Level 1 | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	680	584
Level 2 | US Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,039	830
Level 2 | U.S. Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	29	5
Level 2 | Foreign Government Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	9,545	6,270
Level 2 | Foreign Corporate Bonds
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	1,951	3,058
Level 2 | Foreign Guaranteed Investment Contract [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	18,120	14,138
Level 2 | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of plan assets	$ 533	$ 239
Japan | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	37.00%
Japan | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	60.00%
Japan | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	3.00%
Korea | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	50.00%
Korea | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	40.00%
Korea | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	10.00%
Philippines | Equity Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	63.00%
Philippines | Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	33.00%
Philippines | Other [Member]
Defined Benefit Plan Disclosure [Line Items]
Plan assets, target allocation (as a percent)	4.00%