Quarterly report pursuant to Section 13 or 15(d)

Long-Term Debt (Details Textual)

v3.8.0.1
Long-Term Debt (Details Textual)
₩ in Thousands
3 Months Ended
Mar. 31, 2018
USD ($)
Apr. 01, 2017
USD ($)
Mar. 31, 2018
KRW (₩)
Dec. 30, 2017
USD ($)
Debt Instrument [Line Items]        
Revolving line of credit       $ 116,000,000
PNC Bank, National Association, as Administrative Agent, and Lender Party [Member]        
Debt Instrument [Line Items]        
Interest expense recognized $ 702,000 $ 725,000    
PNC Bank, National Association, as Administrative Agent, and Lender Party [Member] | Revolving Credit Facility [Member]        
Debt Instrument [Line Items]        
Credit facilities, maximum capacity 300,000,000      
Revolving line of credit 0     116,000,000
Additional credit available subject to pro forma compliance with debt covenant 300,000,000     $ 184,000,000
Shinhan Bank [Member] | Term Loan [Member]        
Debt Instrument [Line Items]        
Credit facilities, maximum capacity $ 932,000   ₩ 1,000,000  
Loan maturity date Mar. 31, 2020      
Variable interest rate on loan 2.05%   2.05%