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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
	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%

X

- 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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X

- Definition

Health Care Cost Trend Rate used to Determine Net Period Benefit Cost

+ References

No definition available.

+ Details

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X

- 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

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X

- 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

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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.

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X

- 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

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- Details

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