Regulatory Matters Regulatory Matters - NPC (Details) - USD ($) $ in Millions	1 Months Ended
	Sep. 30, 2016	Dec. 31, 2015
Schedule Of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities	$ 2,788	$ 2,631
Accounts Payable, Current	1,475	1,564
Nevada Power Company [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Regulatory liabilities	411	304
Accounts Payable, Current	208	$ 214
Nevada Chapter 704B, Impact Fees [Member] | Nevada Power Company [Member]
Schedule Of Regulatory Assets and Liabilities [Line Items]
Deferred Revenue, Additions	97
Regulatory liabilities	92
Accounts Payable, Current	$ 5