Annual report pursuant to Section 13 and 15(d)

Short-Term Borrowings and Credit Lines (Narrative) (Details)

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Short-Term Borrowings and Credit Lines (Narrative) (Details)
 12 Months Ended
Dec. 31, 2019
CAD ($)
Dec. 31, 2019
EUR (€)
Dec. 31, 2019
JPY (¥)
Dec. 31, 2019
USD ($)
Dec. 31, 2018
USD ($)
Line of Credit Facility [Line Items]          
Available credit amount       $ 50,000,000.0  
Committed Line Of Credit [Member]          
Line of Credit Facility [Line Items]          
Long-term Line of Credit       0  
Canadian Subsidiary [Member] | Unsecured And Uncommitted Line Of Credit [Member]          
Line of Credit Facility [Line Items]          
Interest rate description Canadian prime rate        
Maximum borrowing capacity $ 30,000,000.0     23,000,000.0  
Long-term Line of Credit       0 $ 0
European Subsidiary [Member] | Unsecured And Uncommitted Line Of Credit [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity       34,500,000  
European Subsidiary [Member] | Unsecured And Uncommitted Credit Line1 [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity | €   € 25,800,000      
European Subsidiary [Member] | Unsecured And Uncommitted Credit Line2 [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity | €   € 5,000,000.0      
Long-term Line of Credit       0 0
Japanese Subsidiary [Member] | Unsecured And Uncommitted Line Of Credit [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity       $ 9,800,000  
Japanese Subsidiary [Member] | Unsecured And Uncommitted Line Of Credit [Member] | Bank Of Tokyo Prime Rate [Member]          
Line of Credit Facility [Line Items]          
Basis points 10000.00% 10000.00% 10000.00% 10000.00%  
Japanese Subsidiary [Member] | Unsecured And Uncommitted Credit Line1 [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity       $ 7,000,000.0  
Japanese Subsidiary [Member] | Unsecured And Uncommitted Credit Line1 [Member] | JPY LIBOR [Member]          
Line of Credit Facility [Line Items]          
Basis points 10000.00% 10000.00% 10000.00% 10000.00%  
Japanese Subsidiary [Member] | Unsecured And Uncommitted Credit Line2 [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity | ¥     ¥ 300,000,000.0    
Long-term Line of Credit       $ 0 0
Korean Subsidiary [Member] | Unsecured And Uncommitted Line Of Credit [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity       20,000,000.0  
China Subsidiary [Member] | Unsecured And Uncommitted Line Of Credit [Member]          
Line of Credit Facility [Line Items]          
Maximum borrowing capacity       20,000,000.0  
Long-term Line of Credit       $ 0 $ 0
Committed Portion Of Credit Facility [Member] | Domestic [Member]          
Line of Credit Facility [Line Items]          
Maturity date of agreement Aug. 01, 2023        
Minimum | Revolving Line Of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]          
Line of Credit Facility [Line Items]          
Basis points 87.50% 87.50% 87.50% 87.50%  
Maximum | Revolving Line Of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]          
Line of Credit Facility [Line Items]          
Basis points 162.50% 162.50% 162.50% 162.50%  
Maximum | European Subsidiary [Member] | Revolving Line Of Credit [Member] | European Central Bank Refinancing Rate [Member]          
Line of Credit Facility [Line Items]          
Basis points 7500.00% 7500.00% 7500.00% 7500.00%  
Maximum | European Subsidiary [Member] | Revolving Line Of Credit [Member] | Euro Overnight Index Average [Member]          
Line of Credit Facility [Line Items]          
Basis points 7500.00% 7500.00% 7500.00% 7500.00%  
Maximum | China Subsidiary [Member] | Unsecured And Uncommitted Line Of Credit [Member] | London Interbank Offered Rate (LIBOR) [Member]          
Line of Credit Facility [Line Items]          
Basis points 180.00% 180.00% 180.00% 180.00%  
Maximum | China Subsidiary [Member] | Unsecured And Uncommitted Line Of Credit [Member] | People's Bank Of China Rate [Member]          
Line of Credit Facility [Line Items]          
Basis points 110.00% 110.00% 110.00% 110.00%