REGULATORY ACTIONS, FERC Matters (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011
NPC [Member]
FERC Matters [Abstract]
Receivable from CAISO and CALPX	$ 19
SPPC [Member]
FERC Matters [Abstract]
Receivable from CAISO and CALPX	1
Additional liability recorded related to receivable	$ 3

Receivable from power sales to the California Independent System Operator (CAISO) and the bankrupt California Power Exchange (CALPX).

No definition available.

Name:	nve_ReceivableFromPowerSales
Namespace Prefix:	nve_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant