Bank indebtedness and Long-Term Debt (Long term debt table) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 29, 2012	Dec. 31, 2011
Debt Instrument [Line Items]
Promissory Notes	$ 0	$ 8,744
Other Long-term Debt	1,541	1,497
Total Long-term and Current Term Debt	(53,760)	(52,264)
Current portion of long-term debt	(5,924)	(35,198)
Total Long-Term Debt	47,836	17,066
US Non Revolving Real Estate Term Facility [Member] \| Syndicate Lending Group [Member]
Debt Instrument [Line Items]
Secured Debt	0	12,133
US Non Revolving Machinery And Equipment Term Facility [Member] \| Syndicate Lending Group [Member]
Debt Instrument [Line Items]
Secured Debt	0	11,078
Non Revolving Term Credit Facility [Member] \| Opta Minerals Inc [Member]
Debt Instrument [Line Items]
Secured Debt	52,219	0
Term Loan Facility [Member] \| Opta Minerals Inc [Member]
Debt Instrument [Line Items]
Secured Debt	0	6,392
Revolving Acquisition Facility [Member] \| Opta Minerals Inc [Member]
Debt Instrument [Line Items]
Secured Debt	$ 0	$ 12,420

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Including current and noncurrent portions, aggregate carrying amount of long-term borrowings as of the balance sheet date. May include notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt, which had initial maturities beyond one year or beyond the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Total of the portions of the carrying amounts as of the balance sheet date of long-term debt, which may include notes payable, bonds payable, debentures, mortgage loans, and commercial paper, which are scheduled to be repaid within one year or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Sum of the carrying values as of the balance sheet date of all long-term debt, which is debt initially having maturities due after one year from the balance sheet date or beyond the operating cycle, if longer, but excluding the portions thereof scheduled to be repaid within one year (current maturities) or the normal operating cycle, if longer, and after deducting unamortized discount or premiums, if any.

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Including both current and noncurrent portions, carrying amount as of the balance sheet date of other forms of debt not elsewhere specified in the taxonomy with initial maturities beyond one year or beyond the normal operating cycle, if longer.

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Including the current and noncurrent portions, the carrying value of notes payable which were initially due after one year or beyond the normal operating cycle, if longer, and which are not otherwise defined in the taxonomy.

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Carrying value as of the balance sheet date , including the current and noncurrent portions, of collateralized debt obligations (with maturities initially due after one year or beyond the operating cycle, if longer). Such obligations include mortgage loans, chattel loans, and any other borrowings secured by assets of the borrower.

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