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Employee Benefit Plans - Postretirement Benefits Other Than Pensions (OPEB) - Additional Information (Detail) - OPEB - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2016 | Dec. 31, 2015 | Dec. 31, 2014
Defined Benefit Plan Disclosure [Line Items] |  |  |
Health care benefits | 65 years |  |
Unrecognized actuarial losses to be recognized in next fiscal year | $ 0.2 |  |
Unrecognized prior service credit to be recognized in next fiscal year | 0.6 |  |
Accumulated benefit obligations (ABO) | $ 7.2 | $ 7.0 | $ 8.5
Discount rate | 3.90% | 3.70% | 4.60%
United States |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Accumulated benefit obligations (ABO) | $ 0.5 | $ 0.6 |
Canada |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Accumulated benefit obligations (ABO) | $ 6.7 | $ 6.4 |

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- Definition The interest rate used to adjust for the time value of money. + 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 1) For defined benefit pension plans, the benefit obligation is the projected benefit obligation, which is the actuarial present value as of a date of all benefits attributed by the pension benefit formula to employee service rendered prior to that date. 2) For other postretirement defined benefit plans, the benefit obligation is the accumulated postretirement benefit obligation, which is the actuarial present value of benefits attributed to employee service rendered to a particular date. + 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 (a) -URI http://asc.fasb.org/extlink&oid=65897934&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Projected Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6522206 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Glossary Accumulated Postretirement Benefit Obligation -URI http://asc.fasb.org/extlink&oid=6503904 + 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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- Definition Amount included in accumulated other comprehensive income (AOCI) related to gain (loss) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position. + References No definition available. + Details
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- Definition Amount included in accumulated other comprehensive income (AOCI) related to prior service cost (credit) expected to be recognized as components of net periodic benefit cost for the fiscal year that follows the most recent annual statement of financial position. + References No definition available. + Details
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- Definition Describes pertinent information about the defined benefit plan that is not otherwise reflected in the taxonomy. + References No definition available. + Details
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