Regulatory Matters Regulatory Matters - NPC - Regulatory Assets (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2016	Dec. 31, 2015
Regulatory Assets [Line Items]
Total regulatory assets		$ 4,457	$ 4,285
Regulatory assets		150	130
Regulatory assets		4,307	4,155
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided		$ 2,800	2,300
Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years	[1]	27 years
Total regulatory assets	[1]	$ 1,754	1,577
Employee benefit plans [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years	[2]	17 years
Total regulatory assets	[2]	$ 816	778
Abandoned Projects [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		3 years
Total regulatory assets		$ 159	136
Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		12 years
Total regulatory assets		$ 301	281
Regulatory assets other [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		Various
Total regulatory assets		$ 856	706
Nevada Power Company [Member]
Regulatory Assets [Line Items]
Total regulatory assets		1,020	1,057
Regulatory assets		20	0
Regulatory assets		1,000	1,057
Remaining Amounts of Regulatory Assets for which No Return on Investment During Recovery Period is Provided		$ 560	572
Nevada Power Company [Member] | Deferred Income Tax Charge [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years	[3]	P27Y
Total regulatory assets	[3]	$ 141	149
Nevada Power Company [Member] | Acquisition-related Costs [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		P28Y
Total regulatory assets		$ 136	143
Nevada Power Company [Member] | Deferred Operating Costs [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		P20Y
Total regulatory assets		$ 127	87
Nevada Power Company [Member] | Decommissioning costs [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		P7Y
Total regulatory assets		$ 114	121
Nevada Power Company [Member] | Employee benefit plans [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years	[4]	P10Y
Nevada Power Company [Member] | Pension and Other Postretirement Plans Costs [Member]
Regulatory Assets [Line Items]
Total regulatory assets	[4]	$ 105	98
Nevada Power Company [Member] | Abandoned Projects [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		P3Y
Total regulatory assets		$ 75	91
Nevada Power Company [Member] | Asset Retirement Obligation Costs [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		P7Y
Total regulatory assets		$ 74	79
Nevada Power Company [Member] | Legacy Meters [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		P16Y
Total regulatory assets		$ 60	64
Nevada Power Company [Member] | Deferred Excess Energy Costs [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		P3Y
Total regulatory assets		$ 40	56
Nevada Power Company [Member] | Regulatory assets other [Member]
Regulatory Assets [Line Items]
Regulatory asset amortization period years		Various
Nevada Power Company [Member] | Other Regulatory Assets (Liabilities) [Member]
Regulatory Assets [Line Items]
Total regulatory assets		$ 148	$ 169

[1] Amounts primarily represent income tax benefits related to state accelerated tax depreciation and certain property-related basis differences that were previously flowed through to customers and will be included in regulated rates when the temporary differences reverse.

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

[3] Amounts represent income tax benefits related to accelerated tax depreciation and certain property-related basis differences that were previously flowed through to customers and will be included in regulated rates when the temporary differences reverse.

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