Leases Leases - NPC - Other (Details) $ in Millions	6 Months Ended
	Jun. 30, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Payments	$ (70)
Finance Lease, Interest Payment on Liability	(22)
Finance Lease, Principal Payments	(9)
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	6
Nevada Power Company [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Payments	(1)
Finance Lease, Interest Payment on Liability	(20)
Finance Lease, Principal Payments	(7)
Right-of-Use Asset Obtained in Exchange for Finance Lease Liability	$ 4