LONG-TERM DEBT, Maturities of Long-Term Debt (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012		Dec. 31, 2011
Long-term Debt, by Maturity [Abstract]
2013	$ 354,848	[1]
2014	324,317
2015	251,746
2016	661,854
2017	1,934
Long-term Debt, maturing through 2016	1,594,699
Thereafter	3,429,751
Long-term debt including current maturities	5,024,450
Debt Instrument, Unamortized (Discount) Premium, Net	1,631		(12,546)
Total	5,026,081
Parent Company [Member]
Long-term Debt, by Maturity [Abstract]
2013	0	[1]
2014	195,000
2015	0
2016	0
2017	0
Long-term Debt, maturing through 2016	195,000
Thereafter	315,000
Long-term debt including current maturities	510,000
Debt Instrument, Unamortized (Discount) Premium, Net			0
Total	510,000
Nevada Power Company [Member]
Long-term Debt, by Maturity [Abstract]
2013	104,613	[1]
2014	129,142
2015	251,567
2016	211,677
2017	1,753
Long-term Debt, maturing through 2016	698,752
Thereafter	2,647,931
Long-term debt including current maturities	3,346,683
Debt Instrument, Unamortized (Discount) Premium, Net	(9,827)		(25,455)
Total	3,336,856
Sierra Pacific Power Company [Member]
Long-term Debt, by Maturity [Abstract]
2013	250,235	[1]
2014	175
2015	179
2016	450,177
2017	181
Long-term Debt, maturing through 2016	700,947
Thereafter	466,820
Long-term debt including current maturities	1,167,767
Debt Instrument, Unamortized (Discount) Premium, Net	11,458		12,909
Total	$ 1,179,225

[1] Amounts may differ from current portion of long-term debt as reported on the consolidated balance sheet due to the timing difference of payments and the change in obligation.