Leases Leases - SPPC - Summary (Details) $ in Millions	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	$ 544
Finance Lease, Right-of-Use Asset	509
Total Right-of-Use Asset	1,053
Operating Lease, Liability	586
Finance Lease, Liability	522
Total Lease Liabilities	1,108
Sierra Pacific Power Company [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	19
Finance Lease, Right-of-Use Asset	38
Total Right-of-Use Asset	57
Operating Lease, Liability	19
Finance Lease, Liability	39
Total Lease Liabilities	$ 58