CONSOLIDATED STATEMENTS OF COMMON SHAREHOLDERS' EQUITY (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	$ 838	$ 202	$ 217
Market value of risk management assets and liabilities	283	369	0
Nevada Power Company [Member]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	208	129	205
Sierra Pacific Power Company [Member]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	$ 81	$ (645)	$ 116