Leases - NPC - Narrative (Details) - USD ($) $ in Millions	1 Months Ended	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2021	Dec. 31, 2020
NPC
Lessee, Lease, Description [Line Items]
Remaining share ownership, transmission tine project		75.00%
ON Line financing lease obligation		$ 286	$ 295
SPPC
Lessee, Lease, Description [Line Items]
Remaining share ownership, transmission tine project		75.00%
ON Line financing lease obligation		$ 110	$ 122
ON Line deferrals | Nevada Utilities
Lessee, Lease, Description [Line Items]
Utilities aggregate share ownership, transmission line project		25.00%
ON Line deferrals | NPC
Lessee, Lease, Description [Line Items]
Utilities aggregate share ownership, transmission line project	95.00%	75.00%
Finance lease term		41 years
ON Line deferrals | SPPC
Lessee, Lease, Description [Line Items]
Utilities aggregate share ownership, transmission line project	5.00%	25.00%
Finance lease term		41 years