Termination of Proposed Acquisition by Hydro One Termination of Proposed Acquisition by Hydro One (Details) - USD ($) $ in Thousands		12 Months Ended
Jan. 24, 2019	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Business Acquisition [Line Items]
Termination Fee Received from Canceled Business Acquisition		$ 103,000	$ 0	$ 0
Merger transaction costs		$ 19,675	$ 3,718	$ 14,618
Hydro One [Member]
Business Acquisition [Line Items]
Termination Fee Received from Canceled Business Acquisition	$ 103,000

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460

Name:	us-gaap_BusinessCombinationAcquisitionRelatedCosts
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration