CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
OTHER INCOME (EXPENSE):
AFUDC-debt	$ 7,493	$ 8,718	$ 23,355
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
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 INCOME (EXPENSE):
AFUDC-debt	5,437	6,770	21,443
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	208	129	205
Sierra Pacific Power Company [Member]
OTHER INCOME (EXPENSE):
AFUDC-debt	2,056	1,948	1,912
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	$ 81	$ (645)	$ 116