Revenue Recognition Provision for Doubtful Accounts (Details) - Accounting Standards Update 2016-13 [Member] $ in Millions	3 Months Ended
Mar. 31, 2020 USD ($)
Cumulative Effect on Retained Earnings, before Tax	$ 5
Energy Services [Member]
Cumulative Effect on Retained Earnings, before Tax	2
CERC Corp [Member]
Cumulative Effect on Retained Earnings, before Tax	$ 5

Amount of the cumulative effect on retained earnings before related income tax effect.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 250
-SubTopic 10
-Section 50
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=109234566&loc=d3e22663-107794

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 860
-SubTopic 50
-Section 50
-Paragraph 5
-URI http://asc.fasb.org/extlink&oid=116651436&loc=d3e122869-111746

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