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Pending Acquisition by Hydro One Pending Acquisition by Hydro One (Details) - Hydro One [Member] - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2017	Jul. 19, 2017
Business Acquisition [Line Items]
Business Acquisition, Share Price		$ 53
Rate Credit to Retail Customers Related to Merger	$ 31.5
Non-Offsettable Rate Credit to Retail Customers Related to Merger	22.0
Termination Fee Payable By Company If Pending Merger Is Terminated Under Certain Circumstances		$ 103.0
ALASKA
Business Acquisition [Line Items]
Rate Credit to Retail Customers Related to Merger	$ 1.0

X

- Definition

The non-offsettable portion of the proposed rate credit that will be refunded to customers related to the proposed merger with Hydro One.

+ References

No definition available.

+ Details

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- Definition

The proposed rate credit that will be refunded to customers related to the proposed merger with Hydro One.

+ References

No definition available.

+ Details

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X

- Definition

Termination fee payable by company or acquirer if pending merger is terminated under certain circumstances.

+ References

No definition available.

+ Details

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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.

+ References

No definition available.

+ Details

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- Definition

Price of a single share of a number of saleable stocks paid or offered to be paid in a business combination.

+ References

No definition available.

+ Details

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- Details

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- Details

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