Acquisitions and Dispositions (Schedule of Major Classes of Assets and Liabilities Reported As Discontinued Operation) (Detail) $ in Millions	Dec. 31, 2018 USD ($)
East Ohio
Business Acquisition [Line Items]
Current assets of discontinued operations	$ 423	[1]
Investments	2
Property, plant and equipment, net	3,669
Regulatory assets	711
Other deferred charges and other assets, including goodwill and intangible assets	1,275
Noncurrent assets of discontinued operations	5,657
Current liabilities of discontinued operations	1,262
Long-term debt	1,300
Deferred income taxes and investment tax credits	716
Regulatory liabilities	747
Other deferred credits and other liabilities	108
Noncurrent liabilities of discontinued operations	2,871
DGP
Business Acquisition [Line Items]
Current assets of discontinued operations	21	[2],[3]
Noncurrent assets of discontinued operations	192	[4]
Current liabilities of discontinued operations	11
Noncurrent liabilities of discontinued operations	$ 25

[1] Includes cash and cash equivalents of $9 million as of December 31, 2018.

[2] Includes cash and cash equivalents of less than $1 million.

[3] Includes cash and cash equivalents of less than a million dollars as of December 31, 2018.

[4] Primarily property, plant and equipment, net.