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Employee future benefits - Composition of Plan Assets (Details) | Dec. 31, 2018 | Dec. 31, 2017
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Employee Benefits [Abstract] |  |
Cash and cash equivalents | 3.00% | 3.00%
Equity securities | 59.00% | 60.00%
Debt securities | 38.00% | 37.00%
Total | 100.00% | 100.00%

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- Definition Cash And Cash Equivalents, Amount Contributed To Fair Value Of Plan Assets, Allocation Percentage + References No definition available. + Details
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- Definition Debt Instruments, Amount Contributed To Fair Value Of Plan Assets, Allocation Percentage + References No definition available. + Details
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- Definition Equity Instruments, Amount Contributed To Fair Value Of Plan Assets, Allocation Percentage + References No definition available. + Details
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- Definition Plan Assets At Fair Value, Allocation Percentage + References No definition available. + Details
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