Effective Income Tax Rate Reconciliation, Share-based Compensation, Excess Tax Benefit, Amount

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- Definition

Represents the percentage of cash that the participant may elect as a deferred dividend equivalent payment under the first option available under the plan.

+ References

No definition available.

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- Definition

Represents the percentage of fully transferable shares of stock that the participant may elect as a deferred dividend equivalent payment for the first option available under the plan.

+ References

No definition available.

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- Definition

Represents the percentage of fully transferable shares of stock that the participant may elect as a deferred grant for the first option available under the plan.

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No definition available.

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- Definition

Represents the percentage of fully transferable shares of stock that the participant may elect as a deferred grant for the second option available under the plan.

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No definition available.

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Percentage of Cash in which Election to Receive Payment May be Made by Participants for Deferrals Option Two

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No definition available.

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- Definition

Represents the number of additional grants to be made during the period on other than stock (or unit) option plans if performance requirements are met.

+ References

No definition available.

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- Definition

Number of performance elements criteria that affect the number of shares received after the end of the specified performance period, if performance criteria conditions are met.

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- Definition

Represents the number of shares issued as a percentage of the target award.

+ References

No definition available.

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Share Based Compensation Arrangement, Percentage of Fully Transferable Shares of Stock in which Election to Receive Payment May be Made by Participants, Option to Receive Cash Payment

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No definition available.

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- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Restricted Stock Units and Stock Granted Additional Disclosures [Abstract]

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- Definition

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
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- Definition

Amount after tax of increase (decrease) to equity or (increase) decrease to net assets, resulting from the cumulative effect adjustment of a new accounting principle applied in the period of adoption.

+ References

No definition available.

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- Definition

Aggregate cash paid by the entity during the period to settle equity instruments granted under equity-based payment arrangements.

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- Definition

Unrecognized cost of unvested share-based compensation awards.

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- Definition

Weighted average period over which unrecognized compensation is expected to be recognized for equity-based compensation plans, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

The total recognized tax benefit related to compensation cost for equity-based payment arrangements recognized in income during the period.

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- Definition

Estimated period over which an employee is required to provide service in exchange for the equity-based payment award, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

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- References

No definition available.

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- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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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).

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- Definition

Amount of cash paid related to share-based compensation liabilities.

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- Definition

Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash.

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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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- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

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- Definition

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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- Definition

Amount of operating expense for routine plant maintenance, repairs and operations of regulated operation.

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-Name Accounting Standards Codification
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Stock-Based Compensation (Details) $ in Thousands	1 Months Ended		3 Months Ended								12 Months Ended
Stock-Based Compensation (Details) $ in Thousands	Feb. 28, 2017 shares	Dec. 31, 2012 shares	Dec. 31, 2017 USD ($) shares	Sep. 30, 2017 USD ($)	Jun. 30, 2017 USD ($)	Mar. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2017 USD ($) performance_criteria shares	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)
Stock-Based Compensation
Stock compensation cumulative effect adjustments							$ 45,855					$ 45,855
Operations and maintenance			$ (266,149)	$ (224,305)	$ (214,013)	$ (219,976)	(208,277)	$ (217,568)	$ (242,279)	$ (243,195)	$ (924,443)	(911,319)	$ (868,377)
Compensation cost that has been charged against income											21,000	19,000	19,000
Total income tax benefit recognized											15,000	10,000	7,000
Total unrecognized compensation cost related to nonvested share-based compensation arrangements granted			$ 12,000								$ 12,000
Expected weighted-average period of recognition of unrecognized compensation cost											2 years
Total fair value of shares vested											$ 22,000	22,000	21,000
Performance Shares
Number of performance element criteria \| performance_criteria											2
Performance period											3 years
Restricted stock unit awards
Stock-Based Compensation
Share-based liabilities paid											$ 4,000	3,000	10,000
Cash flow effect, cash used to settle awards											$ 4,000	3,000	3,000
Restricted Stock Units, Stock Grants and Stock Units
Vesting period											4 years
Percentage of cash that the participant may elect as a dividend for the first option available under the plan											50.00%
Percentage of stock that the participant may elect as dividend under second option of plan											50.00%
Restricted Stock Units, Stock Grants, and Stock Units
Restricted Stock Units, Stock Grants and Stock Units
Granted (in shares) \| shares											161,963
Shares released during period (in shares) \| shares											3,607
Performance Shares
Stock-Based Compensation
Share-based liabilities paid													$ 16,000
Restricted Stock Units, Stock Grants and Stock Units
Granted (in shares) \| shares											147,706
Shares released during period (in shares) \| shares											4,798
Performance Shares \| Maximum
Performance Shares
Exact number of shares issued as a percentage of the target award											200.00%
Performance Shares \| Minimum
Performance Shares
Exact number of shares issued as a percentage of the target award											0.00%
Officers and Key Employees \| Restricted stock unit awards
Restricted Stock Units, Stock Grants and Stock Units
Percentage of fully transferable shares of stock that the participant may elect as a deferral for the first option available under the plan											100.00%
Percentage of fully transferable shares of stock in that participant may receive cash											100.00%
Chief Executive Officer \| Retention units
Restricted Stock Units, Stock Grants and Stock Units
Granted (in shares) \| shares		50,617
Additional shares to be granted as retention award if performance requirements are met \| shares		33,745
Shares released during period (in shares) \| shares	84,362
Non-Officer Board of Director Member \| Restricted stock unit awards
Restricted Stock Units, Stock Grants and Stock Units
Percentage of fully transferable shares of stock that the participant may elect as a deferral for the first option available under the plan											100.00%
Percentage of cash that the participant may elect as a dividend for the first option available under the plan											50.00%
Percentage of stock that the participant may elect as dividend under second option of plan											50.00%
Percentage of cash that the participant may elect as a dividend equivalent deferral for the first option available under the plan											50.00%
Percentage of fully transferable shares of stock that the participant may elect as a dividend equivalent deferral for the first option available under the plan											50.00%
2012 Plan
Stock-Based Compensation
Common shares available for grant (in shares) \| shares			4,600,000								4,600,000
Common shares available for issuance (in shares) \| shares			2,200,000								2,200,000
Retained Earnings
Stock-Based Compensation
Stock compensation cumulative effect adjustments							5,475					5,475
Accounting Standards Update 2016-09
Stock-Based Compensation
Operations and maintenance												12,000
Accounting Standards Update 2016-09 \| Retained Earnings
Stock-Based Compensation
Stock compensation cumulative effect adjustments							6,000					$ 6,000
Net income tax expense							$ 3,000