Leases Leases - SPPC - Summary (Details) $ in Millions	Sep. 30, 2019 USD ($)
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
Sierra Pacific Power Company [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	18
Finance Lease, Right-of-Use Asset	41
Total Right-of-Use Asset	59
Operating Lease, Liability	18
Finance Lease, Liability	42
Total Lease Liabilities	$ 60