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Summary of Significant Accounting Policies Concentration Risk (Details)	12 Months Ended
	Dec. 31, 2019 USD ($) Employee Customer	Dec. 31, 2018	Dec. 31, 2017
Concentration risk:
Current liabilities exceeding current assets | $	$ 22,609,000
Sales Revenue, Total [Member] | Customer Concentration Risk [Member]
Concentration risk:
Number of major customers, Sales | Customer	4
Concentration Risk, Percentage	62.00%	65.00%	65.00%
Sales Revenue, Total [Member] | Geographic concentration risk | Mexico and Canada [Member]
Concentration risk:
Concentration Risk, Percentage	34.00%	32.00%	36.00%
Accounts Receivable [Member] | Customer Concentration Risk [Member]
Concentration risk:
Concentration Risk, Accounts Receivable, Number of major customers | Customer	4
Concentration Risk, Percentage	49.00%	64.00%
Number of employees, geographic area | Labor force concentration risk
Concentration risk:
Concentration risk, number of employees	1,821
Number of employees, geographic area | Labor force concentration risk | MEXICO
Concentration risk:
Concentration risk, number of employees	795
Number of employees, geographic area | Labor force concentration risk | UNITED STATES
Concentration risk:
Concentration risk, number of employees	764
Number of employees, geographic area | Labor force concentration risk | CANADA
Concentration risk:
Concentration risk, number of employees	262
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | International Association of Machinists and Aerospace Workers
Concentration risk:
Concentration risk, number of employees	341
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | Sindicato de Jorneleros y Obreros
Concentration risk:
Concentration risk, number of employees	635
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | United Food & Commercial Workers Canada [Member] [Member]
Concentration risk:
Concentration risk, number of employees	216
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | Sindicato de trabajadores de la industria metalica y del comercio del estado de Nuevo Leon Presidente Benito Juarez Garcia C.T.M. [Member]
Concentration risk:
Concentration risk, number of employees	35

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