Leases Leases - SPPC - Lease Costs (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Variable Lease, Cost	$ 144
Operating Lease, Cost	41
Finance Lease, Right-of-Use Asset, Amortization	4
Finance Lease, Interest Expense	11
Short-term Lease, Cost	1
Lease, Cost	$ 201
Operating Lease, Weighted Average Remaining Lease Term	7 years 6 months
Finance Lease, Weighted Average Remaining Lease Term	29 years 6 months
Operating Lease, Weighted Average Discount Rate, Percent	5.30%
Finance Lease, Weighted Average Discount Rate, Percent	8.70%
Sierra Pacific Power Company [Member]
Lessee, Lease, Description [Line Items]
Variable Lease, Cost	$ 15
Operating Lease, Cost	0
Finance Lease, Right-of-Use Asset, Amortization	1
Finance Lease, Interest Expense	1
Lease, Cost	$ 17
Operating Lease, Weighted Average Remaining Lease Term	25 years 8 months 12 days
Finance Lease, Weighted Average Remaining Lease Term	23 years 9 months 18 days
Operating Lease, Weighted Average Discount Rate, Percent	4.90%
Finance Lease, Weighted Average Discount Rate, Percent	7.30%