Cumulative Dividend Equivalent Rights Converted to Deferred Restricted Stock Awards

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Dividend Equivalent Rights [Abstract]

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- Definition

Employee Stock Purchase Plan [Abstract]

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Increase (decrease) in liability for stock compensation recorded against retained earnings for dividend equivalent rights.

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- Definition

Restricted Stock Awards, Performance-based, Issued, Intrinsic Value

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Restricted Stock Awards, Performance-based, Outstanding Balance

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- Definition

Restricted Stock Awards, Performance-based, Vested Balance

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- Definition

Number of shares reserved for issuance under equity instrument agreements awarded that validly exist and are outstanding, including vested instruments.

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Cumulative number of shares issued pursuant to the Plan.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested, Grant Date Fair Value

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- Definition

Amount of cost not yet recognized for nonvested award under share-based payment arrangement.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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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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- Definition

The highest percentage of annual salary that an employee is permitted to utilize with respect to the plan.

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Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
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- Definition

The highest quantity of shares an employee can purchase under the plan per period.

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- Definition

Number of non-option equity instruments exercised by participants.

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- Definition

Number of shares under non-option equity instrument agreements that were either cancelled or expired.

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Net number of non-option equity instruments granted to participants.

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- Definition

Number of equity instruments other than options outstanding, including both vested and non-vested instruments.

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Number of shares authorized for issuance under share-based payment arrangement.

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

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Percentage of vesting of award under share-based payment arrangement.

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- Definition

Purchase price of common stock expressed as a percentage of its fair value.

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Number of shares issued during the period as a result of an employee stock purchase plan.

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Amount of noncash expense for option under share-based payment arrangement.

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Equity Plans Equity Plans - Narrative (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Option Indexed to Issuer's Equity [Line Items]
Fair value of restricted stock awards	$ 3,333	$ 2,420	$ 1,913
Performance-based and market-based restricted stock awards issued (in shares)	5,327	6,120	52,629
Performance-based and market-based restricted stock awards vested (in shares)	16,544
Performance-based and market-based restricted stock awards outstanding (in shares)	43,257
Employee Stock Purchase Plan [Abstract]
Shares issued during the period under the plan	31,750	30,255	25,907
Restricted Stock and Deferred Restricted Stock
Option Indexed to Issuer's Equity [Line Items]
Unrecognized compensation cost	$ 4,118
Period for recognition of compensation cost	1 year 8 months 26 days
Deferred Restricted Stock Awards
Dividend Equivalent Rights [Abstract]
Cumulative dividend equivalent rights converted to deferred restricted stock awards (in shares)	83,679	81,231	79,478
Dividend Equivalent Rights
Dividend Equivalent Rights [Abstract]
Liability for dividend equivalent rights	$ 160	$ 93	$ 97
Performance Shares \| Minimum
Option Indexed to Issuer's Equity [Line Items]
Range of shares issuable	0.00%
Performance Shares \| Maximum
Option Indexed to Issuer's Equity [Line Items]
Range of shares issuable	150.00%
Market-Based Restricted Stock Awards \| Minimum
Option Indexed to Issuer's Equity [Line Items]
Range of shares issuable	0.00%
Market-Based Restricted Stock Awards \| Maximum
Option Indexed to Issuer's Equity [Line Items]
Range of shares issuable	200.00%
Incentive Plan \| Restricted Stock and Deferred Restricted Stock
Option Indexed to Issuer's Equity [Line Items]
Issued (in shares)	68,995
Exercised (in shares)	61,155
Forfeited (in shares)	4,498
Outstanding (in shares)	178,106	174,764
CTWS Plan
Option Indexed to Issuer's Equity [Line Items]
Number of shares reserved for issuance under the plan (in shares)	156,022
CTWS Plan \| Restricted Stock and Deferred Restricted Stock
Option Indexed to Issuer's Equity [Line Items]
Issued (in shares)	1,701
Exercised (in shares)	47,583
Forfeited (in shares)	0
Outstanding (in shares)	57,049
Employee Stock Purchase Plan
Option Indexed to Issuer's Equity [Line Items]
Unrecognized compensation cost	$ 160
Employee Stock Purchase Plan [Abstract]
Purchase price of common stock to employees under the plan, percent	85.00%
Maximum percent of base salary employees can designate for share purchase under the plan	10.00%
Expenses recorded under the plan	$ 342	$ 294	$ 265
Common Stock \| Incentive Plan
Option Indexed to Issuer's Equity [Line Items]
Number of shares reserved for issuance under the plan (in shares)	1,800,000
Maximum number of shares per employee (in shares)	600,000
Shares issued pursuant to the plan (in shares)	880,495	819,340	793,811
Shares issuable under the plan upon exercise of outstanding awards (in shares)	178,106	174,764	124,275
Number of shares available for grant (in shares)	741,399
Common Stock \| Employee Stock Purchase Plan
Option Indexed to Issuer's Equity [Line Items]
Number of shares reserved for issuance under the plan (in shares)	400,000
Number of shares available for grant (in shares)	220,813