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Employee Benefit Plans - Summary of Weighted-Average Assumptions for Disclosure (Detail) - Supplemental Employee Retirement Plan [Member]	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Weighted-average assumptions for Disclosure
Discount rate	2.10%	2.95%
Mortality table	Pri-2012 WC	Pri-2012
mortality improvement scale	MP-2020	MP-2019

X

- Definition

Defined benefit plan description of mortality.

+ References

No definition available.

+ Details

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X

- Definition

Defined benefit plan description of mortality improvement scale.

+ 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 benefit obligation 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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- References

No definition available.

+ Details

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- Details

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