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Pension and other postretirement benefits - Weighted Average assumptions used in calculating benefit obligations (Details) | Dec. 31, 2016 | Dec. 31, 2015
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Defined Benefit Pension Plans [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |
Discount rate | 4.19% | 4.44%
Rate of compensation increase, group 1 | 3.00% | 3.00%
Rate of compensation increase, group 2 | 4.00% | 4.00%
Other Postretirement Benefit Plans [Member] |  |
Defined Benefit Plans and Other Postretirement Benefit Plans [Line Items] |  |
Discount rate | 4.20% | 4.50%
Rate of compensation increase, group 1 | 3.00% | 3.00%
Rate of compensation increase, group 2 | 4.00% | 4.00%

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- Definition The maximum expected rate of compensation increases (for pay-related plans). + References No definition available. + Details
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- Definition The interest rate used to adjust for the time value of money for the plan. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Expected rate of compensation increases (for pay-related plans). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(2) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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- Details
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