CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (Parenthetical) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
OTHER INCOME (EXPENSE):
AFUDC-debt	$ 1,976	$ 1,326	$ 5,479	$ 10,371
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	(74)	(293)	(246)	(1,302)
Market value of risk management assets and liabilities	91	0	355	0
Nevada Power Company [Member]
OTHER INCOME (EXPENSE):
AFUDC-debt	1,528	842	4,021	8,962
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	(33)	(41)	(103)	(554)
Sierra Pacific Power Company [Member]
OTHER INCOME (EXPENSE):
AFUDC-debt	448	484	1,458	1,409
Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest [Abstract]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Tax	$ (22)	$ (150)	$ (68)	$ (1,201)