Risk Management and Hedging Activities - NPC - Balance Sheet Location (Details) - Commodity derivative [Member] - USD ($) $ in Millions		Sep. 30, 2016	Jun. 30, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Dec. 31, 2014
Not Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		$ 233		$ 292
Net Regulatory Asset (Liability), Unrealized Loss (Gain) On Derivative Contracts		195	$ 185	250	$ 253	$ 233	$ 223
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		66		113
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		164		175
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]	9		8
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]	10		14
Recurring [Member] | Nevada Power Company [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		19		22
Recurring [Member] | Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability Including Not Subject to Master Netting Arrangement		32		46
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]	19		22
Net Regulatory Asset (Liability), Unrealized Loss (Gain) On Derivative Contracts		$ 19		$ 22

[1] (1)Nevada Power's commodity derivatives not designated as hedging contracts are included in regulated rates and as of September 30, 2016 and December 31, 2015, a regulatory asset of $19 million and $22 million, respectively, was recorded related to the derivative liability of $19 million and $22 million, respectively.