TSR Liability Awards (Details) shares in Thousands, $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($) Parties shares	Dec. 31, 2018 USD ($) shares	Dec. 31, 2017 USD ($) shares
Equity Instruments Other than Options Activity [Roll Forward]
Granted (in shares)	483	500	503
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Award Vesting Period (in years)	3 years
Number of Utilities in Peer Group \| Parties	20
TSR Liability Awards
Equity Instruments Other than Options Activity [Roll Forward]
Granted (in shares)	225	239	240
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Award Vesting Period (in years)	3 years
Amount of cash used to settle TSR liability awards \| $	$ 21,000
Awards settled (in shares)	466	482	454
Settlement amount (cash and common stock) \| $	$ 24,930	$ 21,534	$ 19,083
TSR Liability Awards \| Minimum
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Percentage payout for TSR liability awards	0.00%
TSR Liability Awards \| Maximum
Equity Instruments Other than Options, Additional Disclosures [Abstract]
Percentage payout for TSR liability awards	200.00%

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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=116856206&loc=d3e5070-113901

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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=116856206&loc=d3e5070-113901

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

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No definition available.

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- Definition

Aggregate value of cash and stock paid by the entity during the period to settle performance share plan (PSP) awards granted under the Company's long-term incentive plan.

+ References

No definition available.

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

+ References

No definition available.

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Number of Utilities in Peer Group

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- Definition

Percentage payout for performance share plan (PSP) liability awards.

+ References

No definition available.

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- Definition

The number of units/shares settled under a share-based award plan during the period in cash or stock.

+ References

No definition available.

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