STOCK-BASED COMPENSATION PLAN - Nonvested Restricted Stock Awards and Fair Value Assumptions (Details)	3 Months Ended
Mar. 31, 2021 $ / shares shares
2019 - TSR \| Officers & Key Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Outstanding (in shares) \| shares	32,292
Fair Value Per Share (in dollars per share) \| $ / shares	$ 32.88
Expected Volatility	23.20%
Risk-Free Interest Rate	2.40%
2019 - CEGR, Time \| Officers & Key Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Outstanding (in shares) \| shares	69,496
Fair Value Per Share (in dollars per share) \| $ / shares	$ 31.38
2020 - TSR \| Officers & Key Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Outstanding (in shares) \| shares	41,306
Fair Value Per Share (in dollars per share) \| $ / shares	$ 25.51
Expected Volatility	34.80%
Risk-Free Interest Rate	0.21%
2020 - CEGR, Time \| Officers & Key Employees
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Outstanding (in shares) \| shares	169,164
Fair Value Per Share (in dollars per share) \| $ / shares	$ 25.19
2020 \| Directors
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Shares Outstanding (in shares) \| shares	1,627
Fair Value Per Share (in dollars per share) \| $ / shares	$ 24.20

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

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)(i)-(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

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- Definition

The estimated measure of the percentage by which a share price is expected to fluctuate during a period. Volatility also may be defined as a probability-weighted measure of the dispersion of returns about the mean. The volatility of a share price is the standard deviation of the continuously compounded rates of return on the share over a specified period. That is the same as the standard deviation of the differences in the natural logarithms of the stock prices plus dividends, if any, over the period.

+ 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 (f)(2)(ii)
-URI http://asc.fasb.org/extlink&oid=120381028&loc=d3e5070-113901

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- Definition

The risk-free interest rate assumption that is used in valuing an option on its own shares.

+ References

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

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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.

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No definition available.

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