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Employee Benefits, Net Periodic Benefit Costs and Charges Relating To All Other Employee Benefit Plans(Details) - USD ($) $ in Millions | 3 Months Ended
--- | ---
Mar. 31, 2018 | Mar. 31, 2017
Salaried VEBA1: |  |
Gain on removal of Union VEBA net assets | $ 0.0 | $ (1.3)
Total other employee benefit plans | 7.1 | 6.0
Fabricated Products |  |
Salaried VEBA1: |  |
Deferred compensation plan | 0.0 | 0.1
Defined contribution plans | 3.8 | 4.1
Multiemployer pension plans | 1.2 | 1.1
Total other employee benefit plans | 5.0 | 5.3
All Other |  |
Salaried VEBA1: |  |
Deferred compensation plan | 0.1 | 0.4
Defined contribution plans | 0.5 | 0.5
Total other employee benefit plans | 2.1 | 0.7
VEBAs | All Other |  |
Salaried VEBA1: |  |
Interest cost | 0.7 | 0.7
Expected return on plan assets | (0.7) | (1.0)
Amortization of prior service cost | 1.3 | 1.2
Amortization of net actuarial loss | 0.2 | 0.2
Total net periodic postretirement benefit cost relating to Salaried VEBA | 1.5 | 1.1
VEBAs | All Other |  |
Salaried VEBA1: |  |
Total net periodic postretirement benefit cost relating to Salaried VEBA | 1.5 | 1.1
Gain on removal of Union VEBA net assets | $ 0.0 | $ (1.3)

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- Definition The compensation expense recognized during the period pertaining to the deferred compensation arrangement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=96867065&loc=d3e5047-113901 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 710 -SubTopic 10 -Section 30 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6409875&loc=d3e20015-108363 + Details
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- Definition Amount of gain (loss) recognized in net periodic benefit (cost) credit of defined benefit 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 (h)(4) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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- Definition Amount of expected return (loss) recognized in net periodic benefit (cost) credit, calculated based on expected long-term rate of return and market-related value of plan assets of defined benefit 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 (h)(3) -URI http://asc.fasb.org/extlink&oid=82843861&loc=d3e1928-114920 + Details
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