Schedule II Consolidated Valuation and Qualifying Accounts (Details) (Allowance for Doubtful Accounts [Member], USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1	$ 8,150	$ 28,684	$ 32,341
Provision charged to income	15,963	15,735	15,551
Amounts written off, less recoveries	(15,365)	(36,269)	(19,208)
Balance at December 31	8,748	8,150	28,684
Nevada Power Company [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1	6,751	26,428	29,375
Provision charged to income	14,764	13,820	13,147
Amounts written off, less recoveries	(13,893)	(33,497)	(16,094)
Balance at December 31	7,622	6,751	26,428
Sierra Pacific Power Company [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at January 1	1,399	2,256	2,966
Provision charged to income	1,199	1,915	2,404
Amounts written off, less recoveries	(1,472)	(2,772)	(3,114)
Balance at December 31	$ 1,126	$ 1,399	$ 2,256