Leases - NPC - Lease Costs (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Lessee, Lease, Description [Line Items]
Variable Lease, Cost	$ 592	$ 623
Operating	151	170
Amortization	18	16
Finance Lease, Interest Expense	40	41
Lease, Cost	$ 821	$ 857
Operating Lease, Weighted Average Remaining Lease Term	7 years 4 months 24 days	7 years 7 months 6 days
Finance Lease, Weighted Average Remaining Lease Term	27 years 6 months	28 years 9 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent	4.50%	5.20%
Finance Lease, Weighted Average Discount Rate, Percent	8.50%	8.60%
Nevada Power Company [Member]
Lessee, Lease, Description [Line Items]
Variable Lease, Cost	$ 434	$ 434
Operating	3	3
Amortization	12	13
Finance Lease, Interest Expense	29	37
Lease, Cost	$ 478	$ 487
Operating Lease, Weighted Average Remaining Lease Term	6 years 6 months	7 years 6 months
Finance Lease, Weighted Average Remaining Lease Term	28 years 8 months 12 days	30 years 7 months 6 days
Operating Lease, Weighted Average Discount Rate, Percent	4.50%	4.50%
Finance Lease, Weighted Average Discount Rate, Percent	8.60%	8.70%