Supplemental Cash Flow Disclosures - NPC (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	$ 1,040	$ 627
Restricted Cash and Cash Equivalents, Current	212	227
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	1,268	883	$ 1,283	$ 1,003
Interest paid, net of amounts capitalized	1,723	1,713	1,715
Accruals related to property, plant and equipment additions	888	823	653
Nevada Power Company [Member]
Condensed Cash Flow Statements, Captions [Line Items]
Cash and cash equivalents	15	111
Restricted Cash and Cash Equivalents, Current	10	10
Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents	25	121	66	$ 290
Interest paid, net of amounts capitalized	126	166	167
Income Taxes Paid	113	117	89
Accruals related to property, plant and equipment additions	$ 49	$ 34	$ 18