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Pension and other post-retirement benefits - Fair Value of Investments by Asset Category (Details) $ in Thousands | Dec. 31, 2018 USD ($)
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Defined Benefit Plan Disclosure [Line Items] |
Allocation percentage | 100.00%
Level 1 |
Defined Benefit Plan Disclosure [Line Items] |
Fair value of plan assets | $ 454,641
Equity securities |
Defined Benefit Plan Disclosure [Line Items] |
Allocation percentage | 75.00%
Equity securities | Level 1 |
Defined Benefit Plan Disclosure [Line Items] |
Fair value of plan assets | $ 338,946
Debt securities |
Defined Benefit Plan Disclosure [Line Items] |
Allocation percentage | 25.00%
Debt securities | Level 1 |
Defined Benefit Plan Disclosure [Line Items] |
Fair value of plan assets | $ 115,695
Other |
Defined Benefit Plan Disclosure [Line Items] |
Allocation percentage | 0.00%
Other | Level 1 |
Defined Benefit Plan Disclosure [Line Items] |
Fair value of plan assets | $ 0

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- Definition Fair value of assets that have been segregated and restricted to provide pension or postretirement benefits. Assets include, but are not limited to, stocks, bonds, other investments, earnings from investments, and contributions by the employer and employees. + 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 (b) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Percentage of fair value of investments (categorized by debt securities, equity securities, real estate and other plan assets) to the fair value of plan assets held. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 5 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e2446-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (d)(1) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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