REGULATORY ACTIONS, FERC Matters (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Nevada Power Company [Member]
FERC Matters [Abstract]
Receivable from CAISO and CALPX		$ 19.0
TransmissionRateCase	11.3
Sierra Pacific Power Company [Member]
FERC Matters [Abstract]
Receivable from CAISO and CALPX		1.0
Additional liability recorded related to receivable		3.0
TransmissionRateCase	$ 3.2