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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Name:	us-gaap_BusinessAcquisitionLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

Termination of Proposed Acquisition by Hydro One Termination of Proposed Acquisition by Hydro One (Details) - Hydro One [Member] - USD ($) $ / shares in Units, $ in Millions	Jan. 24, 2019	Jul. 19, 2017
Business Acquisition [Line Items]
Business Acquisition, Share Price		$ 53
Subsequent Event [Member]
Business Acquisition [Line Items]
Termination Fee Received from Canceled Business Acquisition	$ 103