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Employee Benefit Plans - Assumptions Used to Calculate Net Periodic Benefit Cost for Domestic Defined Benefit Pension and Postretirement Benefit Plans (Detail) | 12 Months Ended
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Dec. 31, 2020 | Dec. 31, 2019 | Dec. 31, 2018
Pre-65 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Health care cost trend rate | 7.00% | 7.00% | 7.30%
Ultimate cost trend rate | 4.50% | 4.50% | 4.50%
Post-65 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Health care cost trend rate | 6.80% | 6.80% | 7.30%
Ultimate cost trend rate | 4.50% | 4.50% | 4.50%
Defined benefit pension plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate | 3.00% | 4.10% | 3.40%
Long-term rate of return on plan assets | 5.50% | 6.00% | 6.00%
Postretirement benefit plans |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Discount rate | 3.00% | 4.10% | 3.40%
Annual increase in Medicare Part B premium | 6.00% | 6.00% | 6.00%

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- Definition Annual increase in Medicare Part B premium used to determine net periodic benefit cost for domestic postretirement benefit plans. + References No definition available. + Details
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- Definition Health Care Cost Trend Rate used to Determine Net Period Benefit Cost + References No definition available. + Details
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- Definition Weighted average rate for present value of future retirement benefits cash flows, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(1) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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- Definition Weighted average rate of return on plan assets, reflecting average rate of earnings expected on existing plan assets and expected contributions, used to determine net periodic benefit cost of defined benefit plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (k)(3) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e2919-114920 + 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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- Definition Ultimate trend rate for health care cost for defined benefit postretirement plan. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (l) -URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920 + Details
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