Regulatory Matters - SPPC - Regulatory Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2019	Dec. 31, 2018
Regulatory Assets [Line Items]
Total regulatory assets		$ 2,881	$ 3,067
Regulatory assets		115	171
Regulatory assets		2,766	2,896
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided		$ 1,400	1,300
Abandoned projects
Regulatory Assets [Line Items]
Regulatory asset amortization period years		3.48275862068966
Total regulatory assets		$ 58	134
Deferred Operating Costs
Regulatory Assets [Line Items]
Regulatory asset amortization period years		11
Total regulatory assets		$ 134	141
Sierra Pacific Power Company [Member]
Regulatory Assets [Line Items]
Total regulatory assets		295	321
Regulatory assets		12	7
Regulatory assets		283	314
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided		$ 168	190
Sierra Pacific Power Company [Member] | Employee benefit plans
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period	[1]	8 years
Total regulatory assets	[1]	$ 107	132
Sierra Pacific Power Company [Member] | Merger costs from 1999 merger
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		27 years
Total regulatory assets		$ 71	74
Sierra Pacific Power Company [Member] | Abandoned projects
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		7 years
Total regulatory assets		$ 24	29
Sierra Pacific Power Company [Member] | Deferred Operating Costs
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		12 years
Total regulatory assets		$ 23	15
Sierra Pacific Power Company [Member] | Losses on reacquired debt
Regulatory Assets [Line Items]
Regulatory Asset, Amortization Period		15 years
Total regulatory assets		$ 17	19
Sierra Pacific Power Company [Member] | Other
Regulatory Assets [Line Items]
Regulatory asset amortization period years		Various
Total regulatory assets		$ 53	$ 52

[1] Represents amounts not yet recognized as a component of net periodic benefit cost that are expected to be included in regulated rates when recognized.