RETIREMENT PLAN AND POST-RETIREMENT BENEFITS (Tables)

12 Months Ended

Dec. 31, 2012

Compensation and Retirement Disclosure [Abstract]

Schedule of Net Funded Status [Table Text Block]

							Other Postretirement
	Pension Benefits					Benefits
	2012		2011			2012		2011
Change in Benefit Obligations
Benefit obligation at January 1	$	842,045	$	806,034		$	152,039	$	163,423
Service cost		17,627		18,427			2,383		2,611
Interest cost		40,912		40,676			7,620		8,360
Plan participants' contributions		-		-			1,814		2,325
Actuarial loss (gain)		107,936		18,552			13,074		(12,525)
Benefits paid		(73,017)		(42,507)	(1)		(11,187)		(12,255)
Plan amendments		-		577			262		-
Special termination benefits		-		286			-		100
Benefit obligation at December 31	$	935,503	$	842,045		$	166,005	$	152,039
Change in Plan Assets
Fair value of plan net assets at January 1	$	811,480	$	729,940		$	93,196	$	93,648
Actual return on plan assets		86,073		78,104			11,140		8,615
Employer contributions		16,511		41,286			7,370		863
Plan participants' contributions		-		-			1,814		2,325
Benefits paid		(73,017)		(37,850)	(1)		(11,187)		(12,255)
Fair value of plan net assets at December 31	$	841,047	$	811,480		$	102,333	$	93,196
Funded Status at December 31(2)	$	(94,456)	$	(30,565)		$	(63,672)	$	(58,843)

Amounts Recognized in Accumulated Other Comprehensive Income and Regulatory Assets

						Other Postretirement
	Pension Benefits				Benefits
	2012		2011		2012		2011
Net actuarial loss	$	(203,942)	$	(238,672)	$	(19,360)	$	(34,501)
Prior service (cost) credit		(60,691)		34,730		(9,474)		15,141
Accumulated other comprehensive loss, pre-tax		(264,633)		(203,942)		(28,834)		(19,360)
Regulatory asset for pension plans		252,114		194,936		28,834		19,360
Accumulated other comprehensive loss, pre-tax, at December 31	$	(12,519)	$	(9,006)	$	-	$	-

Amortization of Regulatory Assets for Pension Plans and Accumulated Other Comprehensive Income Into Net Periodic Cost

			Other
	Pension		Postretirement
	Benefits		Benefits
Actuarial loss	$	(19,188)	$	(3,561)
Prior service cost	$	(2,882)	$	(3,809)

Schedule of Accumulated Benefit Obligations in Excess of Fair Value of Plan Assets [Table Text Block]

	2012		2011
Projected benefit obligation, end of year	$	935,503	$	842,045
Accumulated benefit obligation, end of year	$	896,988	$	813,101
Fair value of plan net assets, end of year	$	841,047	$	811,480

Schedule of Allocation of Plan Assets [Table Text Block]

2012 Pension Plan Assets
Asset Category			Level 1		Level 2		Level 3		Total
Cash & Cash equivalents(1)			$	376	$	49,580	$	-	$	49,956
Equity:
	U.S. Equity Securities(2)			63,538		166,702		-		230,240
	International Equity Securities			63,936		-		-		63,936
Fixed Income:
	U.S. Preferred Securities			75		-		-		75
	International Preferred Securities			1,382		-		-		1,382
	U.S. Fixed Income Securities(4)			125,165		372,290		-		497,455
	International Fixed Income Securities			4,957		36,669		-		41,626
Other:
	U.S. Future Contracts			(47)		-		-		(47)
	Administrative Trust Net Liabilities(5)			(43,576)		-		-		(43,576)
		Total Pension Plan Assets	$	215,806	$	625,241	$	-	$	841,047

2012 Other Postretirement Benefit Assets
Asset Category			Level 1		Level 2		Level 3		Total
Cash & Cash equivalents(1)			$	1,978	$	1,362	$	-	$	3,340
Equity:
	U.S. Equity Securities(2)			44,296		4,581		-		48,877
	International Equity Securities			1,757		-		-		1,757
Fixed Income:
	U.S. Preferred Securities			2		-		-		2
	International Preferred Securities			38		-		-		38
	U.S. Fixed Income Securities(4)			12,152		36,222		-		48,374
	International Fixed Income Securities			136		1,008		-		1,144
Other:
	U.S. Future Contracts			(1)		-		-		(1)
	Administrative Trust Net Liabilities(5)			(1,198)		-		-		(1,198)
		Total Other Postretirement Benefit Assets	$	59,160	$	43,173	$	-	$	102,333

2011 Pension Plan Assets
Asset Category			Level 1		Level 2		Level 3		Total
Cash & Cash equivalents (1)			$	4,795	$	39,431	$	-	$	44,226
Equity:
	U.S. Equity Securities (3)			52,204		101,231		-		153,435
	International Equity Securities			110,837		-		-		110,837
Fixed Income:
	U.S. Preferred Securities			64		-		-		64
	International Preferred Securities			842		-		-		842
	U.S. Fixed Income Securities (4)			98,311		339,816		-		438,127
	International Fixed Income Securities			3,135		51,902		-		55,037
Other:
	U.S. Future Contracts			(92)		-		-		(92)
	Administrative Trust Net Assets (5)			9,004		-		-		9,004
		Total Pension Plan Assets	$	279,100	$	532,380	$	-	$	811,480

2011 Other Postretirement Benefit Assets
Asset Category			Level 1		Level 2		Level 3		Total
Cash & Cash equivalents (1)			$	105	$	2,756	$	-	$	2,861
Equity:
	U.S. Equity Securities (3)			42,848		2,200		-		45,048
	International Equity Securities			2,409		-		-		2,409
Fixed Income:
	U.S. Preferred Securities			1		-		-		1
	International Preferred Securities			18		-		-		18
	U.S. Fixed Income Securities (4)			10,168		31,301		-		41,469
	International Fixed Income Securities			68		1,128		-		1,196
Other:
	U.S. Future Contracts			(2)		-		-		(2)
	Administrative Trust Net Assets (5)			196		-		-		196
		Total Other Postretirement Benefit Assets	$	55,811	$	37,385	$	-	$	93,196

Schedule of Assumptions Used [Table Text Block]

	Benefit Obligations			Net Periodic Benefit Costs
	2012		2011	2012	2011	2010
Discount rate-pension	4.01	%	4.91%	4.91%	5.09%	5.79%
Discount rate-other benefits	4.09	%	5.09%	5.09%	5.20%	5.75%
Rate of compensation increase	4.00	%	4.00%	4.00%	4.00%	4.50%
Expected long-term return on plan assets-pension	N/A		N/A	6.15%	6.75%	6.75%
Expected long-term return on plan assets-other benefits	N/A		N/A	6.15-7.1%	6.75-7.1%	6.75-7.1%
Initial health care cost trend rate	7.75	%	8.00%	8.00%	8.00%	8.00%
Ultimate health care cost trend rate	4.75	%	4.75%	4.75%	4.75%	5.00%
Number of years to ultimate trend rate	6		7	7	8	7

Schedule of Effect of One-Percentage-Point Change in Assumed Health Care Cost Trend Rates [Table Text Block]

Assumed health care cost trend rates have a significant effect on the amounts reported for the health care plans. A one-percentage-point change in assumed health care cost trend rates would have the following effect:

	1-Percentage		1-Percentage
	Point Increase		Point Decrease
Effect on the postretirement benefit obligation	$	7,260	$	(5,801)
Effect on total of service and interest cost components	$	552	$	(433)

Schedule of Net Benefit Costs [Table Text Block]

NVE
		Pension Benefits						Other Postretirement Benefits
		2012		2011		2010		2012		2011		2010
Service cost		$	17,627	$	18,427	$	18,910	$	2,383	$	2,611	$	2,466
Interest cost			40,912		40,676		42,872		7,620		8,360		8,736
Expected return on plan assets			(49,789)		(48,767)		(44,275)		(6,253)		(6,386)		(6,223)
Amortization of:
	Prior service (credit)/cost		(2,897)		(2,952)		(1,794)		(3,947)		(3,947)		(3,890)
	Actuarial (gain)/loss		13,891		16,620		15,106		2,924		4,333		4,342
Total net benefit cost		$	19,744	$	24,004	$	30,819	$	2,727	$	4,971	$	5,431

NPC
		Pension Benefits						Other Postretirement Benefits
		2012		2011		2010		2012		2011		2010
Service cost		$	9,429	$	9,781	$	9,567	$	1,400	$	1,454	$	1,413
Interest cost			19,524		19,521		20,092		2,409		2,459		2,474
Expected return on plan assets			(24,948)		(24,677)		(21,447)		(2,366)		(2,360)		(2,270)
Amortization of:
	Prior service (credit)/cost		(1,823)		(1,879)		(1,733)		916		916		946
	Actuarial (gain)/loss		5,452		6,758		7,056		883		1,208		1,199
Total net benefit cost		$	7,634	$	9,504	$	13,535	$	3,242	$	3,677	$	3,762

SPPC
		Pension Benefits						Other Postretirement Benefits
		2012		2011		2010		2012		2011		2010
Service cost		$	6,781	$	7,361	$	8,016	$	910	$	1,086	$	977
Interest cost			20,173		20,050		21,557		5,131		5,830		6,187
Expected return on plan assets			(23,751)		(22,964)		(21,723)		(3,763)		(3,905)		(3,844)
Amortization of:
	Prior service (credit)/cost		(1,108)		(1,108)		(104)		(4,878)		(4,878)		(4,851)
	Actuarial (gain)/loss		8,105		9,647		7,876		2,014		3,092		3,109
Total net benefit cost		$	10,200	$	12,986	$	15,622	$	(586)	$	1,225	$	1,578

Schedule of Expected Benefit Payments [Table Text Block]

			Other			Expected
	Pension Benefit		Postretirement			Federal
	Payments		Benefit Payments			Subsidy
2013	$	57,488	$	9,497	$	-
2014		59,705		9,891		-
2015		58,211		9,974		-
2016		66,837		10,108		-
2017		56,057		10,052		-
2018-2022		311,999		49,872		-