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Summary of Significant Accounting Policies - Concentration Risk (Details)	12 Months Ended
	Dec. 31, 2012 Customer	Dec. 31, 2011 Customer
Customer concentration risk
Concentration risk:
Number of major customers	2	2
Accounts receivable | Customer concentration risk
Concentration risk:
Concentration risk percentage	75.00%	77.00%
Sales | Customer concentration risk
Concentration risk:
Concentration risk percentage	74.00%	80.00%
Sales | Geographic concentration risk | Mexico and Canada
Concentration risk:
Concentration risk percentage	28.00%	24.00%
Number of employees, geographic area | Labor force concentration risk
Concentration risk:
Concentration risk, number of employees	1,373
Number of employees, geographic area | Labor force concentration risk | Mexico
Concentration risk:
Concentration risk, number of employees	867
Number of employees, geographic area | Labor force concentration risk | United States
Concentration risk:
Concentration risk, number of employees	506
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk
Concentration risk:
Concentration risk, number of employees	1,373
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | International Association of Machinists and Aerospace Workers
Concentration risk:
Concentration risk, number of employees	154
Workforce subject to collective bargaining arrangements | Unionized employees concentration risk | Sindicato de Jorneleros y Obreros
Concentration risk:
Concentration risk, number of employees	764

X

- Definition

Concentration Risk, Number of Employees

+ References

No definition available.

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- Definition

Concentration Risk, Number of Significant Customers

+ References

No definition available.

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- Definition

For an entity that discloses a concentration risk in relation to quantitative amount, which serves as the "benchmark" (or denominator) in the equation, this concept represents the concentration percentage derived from the division.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 18

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6351-108592



Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 21

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13537-108611



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 275

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=6927468&loc=d3e6404-108592



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 20

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13531-108611

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