REGULATORY ACTIONS, Settled Regulatory Actions (Details) (SPPC Gas [Member], USD $) In Millions, unless otherwise specified	Jun. 30, 2012
SPPC Gas [Member]
Settled Regulatory Actions [Abstract]
Requested rate increase (decrease)	$ 0.2

The amount of requested rate increase (decrease) in the Deferred Energy Accounting Adjustment application filed with the applicable Utilities Commission.

No definition available.

Name:	nve_RequestedDeaaRateIncreaseDecrease
Namespace Prefix:	nve_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant