Recent Financing Transactions Recent Financing Transactions - NPC (Details) - Subsidiary Debt [Member] - Nevada Power Company [Member] - NVE Holdings [Member] - USD ($) $ in Millions	Mar. 31, 2020	Jan. 31, 2020
Mortgage Securities, 2.400%, Series DD due 2030 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 425	$ 425
Debt Instrument, Interest Rate, Stated Percentage	2.40%	2.40%
Mortgage Securities, 3.125%, Series EE due 2050 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 300	$ 300
Debt Instrument, Interest Rate, Stated Percentage	3.125%	3.125%
Mortgage Securities, 2.750%, Series BB due 2020 [Member]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 575	$ 575
Debt Instrument, Interest Rate, Stated Percentage	2.75%	2.75%