CONSOLIDATED BALANCE SHEETS (Parenthetical) (USD $) In Thousands, except Share data, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Current Assets:
Allowance for Doubtful Accounts Receivable, Current	$ 6,533	$ 8,748
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common stock, shares authorized (in shares)	350,000,000	350,000,000
Common stock, shares issued (in shares)	235,999,750	235,999,750
Common stock, shares outstanding (in shares)	235,526,514	235,079,156
Treasury stock (in shares)	473,236	920,594
Nevada Power Company [Member]
Current Assets:
Allowance for Doubtful Accounts Receivable, Current	5,580	7,622
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Common Stock, Par or Stated Value Per Share	$ 1	$ 1
Common stock, shares authorized (in shares)	1,000	1,000
Common stock, shares issued (in shares)	1,000	1,000
Common stock, shares outstanding (in shares)	1,000	1,000
Sierra Pacific Power Company [Member]
Current Assets:
Allowance for Doubtful Accounts Receivable, Current	$ 953	$ 1,126
Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract]
Common Stock, Par or Stated Value Per Share	$ 3.75	$ 3.75
Common stock, shares authorized (in shares)	20,000,000	20,000,000
Common stock, shares issued (in shares)	1,000	1,000
Common stock, shares outstanding (in shares)	1,000	1,000