Risk Management and Hedging Activities - NPC - Balance Sheet Location (Details) - Commodity derivative [Member] - USD ($) $ in Millions		Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016		Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		$ 199		$ 206
Net Regulatory Asset (Liability), Unrealized Loss (Gain) On Derivative Contracts		162	$ 180	148		$ 185	$ 253	$ 250
Not Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		55		46
Not Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		139		150
Nevada Power Company [Member] | Not Designated as Hedging Instrument [Member] | Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[1]	3		7
Nevada Power Company [Member] | Not Designated as Hedging Instrument [Member] | Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[1]	1		7
Recurring [Member] | Nevada Power Company [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		4		14
Recurring [Member] | Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		15		27
Recurring [Member] | Level 3 [Member] | Nevada Power Company [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement	[1]	4		14
Net Regulatory Asset (Liability), Unrealized Loss (Gain) On Derivative Contracts		$ 4		$ 14	[1]

[1] (1)Nevada Power's commodity derivatives not designated as hedging contracts are included in regulated rates and as of June 30, 2017 and December 31, 2016, a regulatory asset of $4 million and $14 million, respectively, was recorded related to the derivative liability of $4 million and $14 million, respectively.