Employee Benefits - Weighted Average Assumptions to Determine Projected Benefit Obligations (Detail)	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Projected Benefit Obligation Assumptions [Member] \| Prior to age 65 [Member]
Health care cost trend rate
Health care cost trend rate	6.25%	6.50%
Projected Benefit Obligation Assumptions [Member] \| After age 65 [Member]
Health care cost trend rate
Health care cost trend rate	6.25%	10.00%
Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	3.40%	4.45%
Cash balance interest crediting rate	3.00%	3.00%
Rate of compensation increase	3.56%	3.52%
Postretirement Welfare Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Discount rate	2.80%	4.05%

No definition available.

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- Definition

Weighted average rate for present value of future retirement benefits cash flows, used to determine benefit obligation of defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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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- Definition

Weighted average rate increase of compensation, used to determine benefit obligation of defined benefit plan. Plan includes, but is not limited to, pay-related defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (k)(2)
-URI http://asc.fasb.org/extlink&oid=118255775&loc=d3e1928-114920

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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.

+ Details

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- Definition

Assumed rate, for next fiscal year, based on annual change in cost of health care cost benefits used to measure expected cost of benefits covered by defined benefit postretirement plan. Factors include, but are not limited to, estimate of health care inflation, change in health care utilization or delivery pattern, technological advances, and change in health status of participant. Excludes factors for change in composition of plan population by age and dependency status.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-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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- Definition

Defined benefit plan assumptions used calculating benefit obligation cash balance interest crediting rate.

+ References

No definition available.

+ Details

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