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Restricted Stock, Performance Share and Cash Awards - Schedule of Restricted Stock Awards Vesting Periods (Detail) - Restricted Stock Units Granted [Member] - shares	3 Months Ended			12 Months Ended
	Mar. 31, 2021	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Vesting Period [Line Items]
Shares granted in the period	314,000	405,870	399,900	326,584	422,610	414,700
Vesting Period One Year [Member]
Vesting Period [Line Items]
Shares granted in the period				10,105	16,740	14,800
Vesting period, years				1 year
Vesting Period Two Years [Member]
Vesting Period [Line Items]
Shares granted in the period				2,105	8,870	12,000
Vesting period, years				2 years
Vesting Period Five Years [Member]
Vesting Period [Line Items]
Shares granted in the period				314,374	397,000	387,900
Vesting period, years				5 years

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- Definition

Vesting Period [Line Items]

+ References

No definition available.

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- Definition

Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)(1)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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