Consolidated Statements of Comprehensive Income (Unaudited) - EEGH (Parenthetical) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Unrecognized amounts on retirement benefits, tax	$ 4	$ 11
Unrealized gains (losses) on cash flow hedges, tax	5	(10)
Eastern Energy Gas Holdings, LLC [Member]
Unrecognized amounts on retirement benefits, tax	0	1
Unrealized gains (losses) on cash flow hedges, tax	$ 3	$ (30)

Amount, after reclassification adjustment, of tax (expense) benefit for (increase) decrease in accumulated other comprehensive income of defined benefit plan.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
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