Leases Leases - NPC - Summary (Details) - USD ($) $ in Millions	Mar. 31, 2019	Dec. 31, 2018
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
Nevada Power Company [Member]
Lessee, Lease, Description [Line Items]
Operating Lease, Right-of-Use Asset	15
Finance Lease, Right-of-Use Asset	449	$ 450
Total Right-of-Use Asset	464
Operating Lease, Liability	18
Finance Lease, Liability	462
Total Lease Liabilities	$ 480