Leases Leases - NPC - Summary (Details) - USD ($) $ in Millions	Sep. 30, 2019	Dec. 31, 2018
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	$ 526
Finance Lease, Right-of-Use Asset	503
Total Right-of-Use Asset	1,029
Operating Lease, Liability	574
Finance Lease, Liability	517
Total Lease Liabilities	1,091
Nevada Power Company [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	14
Finance Lease, Right-of-Use Asset	442	$ 450
Total Right-of-Use Asset	456
Operating Lease, Liability	17
Finance Lease, Liability	454
Total Lease Liabilities	$ 471