Retirement Plans and Other Benefits (Tables)

12 Months Ended

Dec. 31, 2014

Compensation and Retirement Disclosure [Abstract]

Schedule of net periodic benefit costs and the portion of these costs charged to expense (including administrative costs and excluding amounts capitalized as overhead construction, billed to electric plant participants or charged or amortized to the regulatory asset)

The following table provides details of the plans’ net periodic benefit costs and the portion of these costs charged to expense (including administrative costs and excluding amounts capitalized as overhead construction, billed to electric plant participants or charged to the regulatory asset or liability) (dollars in thousands):

	Pension									Other Benefits
	2014			2013			2012			2014			2013			2012
Service cost-benefits earned during the period	$	53,080		$	64,195		$	63,502		$	18,139		$	23,597		$	27,163
Interest cost on benefit obligation	129,194			112,392			119,586			41,243			41,536			46,467
Expected return on plan assets	(158,998		)	(146,333		)	(140,979		)	(46,400		)	(45,717		)	(45,793		)
Amortization of:
Transition obligation	—			—			—			—			—			452
Prior service cost (credit)	869			1,097			1,143			(9,626		)	(179		)	(179		)
Net actuarial loss	10,963			39,852			44,250			1,175			11,310			20,233
Net periodic benefit cost	$	35,108		$	71,203		$	87,502		$	4,531		$	30,547		$	48,343
Portion of cost charged to expense	$	21,985		$	38,968		$	36,333		$	6,000		$	18,469		$	19,321

Schedule of changes in the benefit obligations and funded status

The following table shows the plans’ changes in the benefit obligations and funded status for the years 2014 and 2013 (dollars in thousands):

	Pension						Other Benefits
	2014			2013			2014			2013
Change in Benefit Obligation
Benefit obligation at January 1	$	2,646,530		$	2,850,846		$	890,418		$	990,418
Service cost	53,080			64,195			18,139			23,597
Interest cost	129,194			112,392			41,243			41,536
Benefit payments	(128,550		)	(125,269		)	(29,054		)	(26,675		)
Actuarial (gain) loss	378,394			(255,634		)	150,188			(138,458		)
Plan amendments	—			—			(388,599		)	—
Benefit obligation at December 31	3,078,648			2,646,530			682,335			890,418
Change in Plan Assets
Fair value of plan assets at January 1	2,264,121			2,079,181			748,339			684,221
Actual return on plan assets	292,992			150,546			105,223			76,995
Employer contributions	175,000			140,500			770			14,438
Benefit payments	(116,709		)	(106,106		)	(19,707		)	(27,315		)
Fair value of plan assets at December 31	2,615,404			2,264,121			834,625			748,339
Funded Status at December 31	$	(463,244	)	$	(382,409	)	$	152,290		$	(142,079	)

Schedule of projected benefit obligation and the accumulated benefit obligation for pension plans with an accumulated obligation in excess of plan assets

The following table shows the projected benefit obligation and the accumulated benefit obligation for pension plans with an accumulated obligation in excess of plan assets as of December 31, 2014 and 2013 (dollars in thousands):

	2014		2013
Projected benefit obligation	$	3,078,648	$	2,646,530
Accumulated benefit obligation	2,873,741		2,469,889
Fair value of plan assets	2,615,404		2,264,121

Schedule of amounts recognized on the Consolidated Balance Sheets

The following table shows the amounts recognized on the Consolidated Balance Sheets as of December 31, 2014 and 2013 (dollars in thousands):

	Pension						Other Benefits
	2014			2013			2014		2013
Noncurrent asset	$	—		$	—		$	152,290	$	—
Current liability	(9,508		)	(10,860		)	—		—
Noncurrent liability	(453,736		)	(371,549		)	—		(142,079		)
Net amount recognized	$	(463,244	)	$	(382,409	)	$	152,290	$	(142,079	)

Schedule of accumulated other comprehensive loss

The following table shows the details related to accumulated other comprehensive loss as of December 31, 2014 and 2013 (dollars in thousands): 

	Pension						Other Benefits
	2014			2013			2014			2013
Net actuarial loss	$	577,976		$	344,540		$	148,006		$	57,816
Prior service cost (credit)	1,203			2,072			(379,269		)	(296		)
APS’s portion recorded as a regulatory (asset) liability	(485,037		)	(265,107		)	230,916			(49,298		)
Income tax expense (benefit)	(36,890		)	(32,204		)	851			(2,528		)
Accumulated other comprehensive loss	$	57,252		$	49,301		$	504		$	5,694

Schedule of estimated amounts that will be amortized from accumulated other comprehensive loss and regulatory assets into net periodic benefit cost

The following table shows the estimated amounts that will be amortized from accumulated other comprehensive loss and regulatory assets into net periodic benefit cost in 2015 (dollars in thousands):

	Pension		Other Benefits
Net actuarial loss	$	28,180	$	5,651
Prior service cost (credit)	595		(37,968		)
Total amounts estimated to be amortized from accumulated other comprehensive loss (gain) and regulatory assets (liabilities) in 2014	$	28,775	$	(32,317	)

Schedule of weighted-average assumptions used for both the pension and other benefits to determine benefit obligations and net periodic benefit costs

The following table shows the weighted-average assumptions used for both the pension and other benefits to determine benefit obligations and net periodic benefit costs:

	Benefit Obligations As of December 31,				Benefit Costs For the Years Ended December 31,
	2014		2013		2014				2013		2012
					January - September		October - December
Discount rate – pension	4.02	%	4.88	%	4.88	%	4.88	%	4.01	%	4.42	%
Discount rate – other benefits	4.14	%	5.10	%	5.10	%	4.41	%	4.20	%	4.59	%
Rate of compensation increase	4.00	%	4.00	%	4.00	%	4.00	%	4.00	%	4.00	%
Expected long-term return on plan assets - pension	N/A		N/A		6.90	%	6.90	%	7.00	%	7.75	%
Expected long-term return on plan assets - other benefits	N/A		N/A		6.80	%	4.25	%	7.00	%	7.75	%
Initial healthcare cost trend rate (pre-65 participants)	7.00	%	7.50	%	7.50	%	7.50	%	7.50	%	7.50	%
Initial healthcare cost trend rate (post-65 participants)	5.00	%	7.50	%	7.50	%	5.00	%	7.50	%	7.50	%
Ultimate healthcare cost trend rate	5.00	%	5.00	%	5.00	%	5.00	%	5.00	%	5.00	%
Number of years to ultimate trend rate (pre-65 participants)	4		4		4		4		4		4
Number of years to ultimate trend rate (post-65 participants)	0		4		4		0		4		4

Schedule of effects of one percentage point change in the assumed initial and ultimate health care cost trend rates

A one percentage point change in the assumed initial and ultimate healthcare cost trend rates would have the following effects (dollars in millions): 

	1% Increase		1% Decrease
Effect on other postretirement benefits expense, after consideration of amounts capitalized or billed to electric plant participants	$	10	$	(4	)
Effect on service and interest cost components of net periodic other postretirement benefit costs	12		(9		)
Effect on the accumulated other postretirement benefit obligation	110		(88		)

Schedule of fair value of pension plan and other postretirement benefit plan assets, by asset category

The fair value of Pinnacle West’s pension plan and other postretirement benefit plan assets at December 31, 2014, by asset category, are as follows (dollars in thousands):

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Other (b)		Balance at December 31, 2014
Pension Plan:
Assets:
Cash and cash equivalents	$	387	$	—	$	—	$	—	$	387
Fixed Income Securities:
Corporate	—		1,162,096		—		—		1,162,096
U.S. Treasury	291,817		—		—		—		291,817
Other (a)	—		113,265		—		—		113,265
Equities:
U.S. Companies	246,387		—		—		—		246,387
International Companies	18,069		—		—		—		18,069
Common and collective trusts:
U.S. Equities	—		127,336		—		—		127,336
International Equities	—		317,167		—		—		317,167
Real estate	—		129,715		—		—		129,715
Partnerships	—		138,337		27,929		—		166,266
Short-term investments and other	—		26,016		—		16,883		42,899
Total Pension Plan	$	556,660	$	2,013,932	$	27,929	$	16,883	$	2,615,404
Other Benefits:
Assets:
Cash and cash equivalents	$	318	$	—	$	—	$	—	$	318
Fixed Income Securities:
Corporate	—		187,961		—		—		187,961
U.S. Treasury	130,967		—		—		—		130,967
Other (a)	—		35,291		—		—		35,291
Equities:
U.S. Companies	265,106		—		—		—		265,106
International Companies	17,813		—		—		—		17,813
Common and collective trusts:
U.S. Equities	—		88,258		—		—		88,258
International Equities	—		85,746		—		—		85,746
Real Estate	—		11,657		—		—		11,657
Short-term investments and other	—		7,408		—		4,100		11,508
Total Other Benefits	$	414,204	$	416,321	$	—	$	4,100	$	834,625

(a) This category consists primarily of debt securities issued by municipalities.

(b) Represents plan receivables and payables.

Schedule of changes in fair value for assets that are measured at fair value on a recurring basis using significant unobservable inputs (Level 3)

The fair value of Pinnacle West’s pension plan and other postretirement benefit plan assets at December 31, 2013, by asset category, are as follows (dollars in thousands):

	Quoted Prices in Active Markets for Identical Assets (Level 1)		Significant Other Observable Inputs (Level 2)		Significant Unobservable Inputs (Level 3)		Other (b)		Balance at December 31, 2013
Pension Plan:
Assets:
Cash and cash equivalents	$	504	$	—	$	—	$	—	$	504
Fixed Income Securities:
Corporate	—		898,621		—		—		898,621
U.S. Treasury	231,590		—		—		—		231,590
Other (a)	—		84,011		—		—		84,011
Equities:
U.S. Companies	239,036		—		—		—		239,036
International Companies	19,429		—		—		—		19,429
Common and collective trusts:
U.S. Equities	—		116,150		—		—		116,150
International Equities	—		367,551		—		—		367,551
Fixed Income	—		137,520		—		—		137,520
Real estate	—		119,739		—		—		119,739
Partnerships	—		—		8,660		—		8,660
Short-term investments and other	—		41,060		—		250		41,310
Total Pension Plan	$	490,559	$	1,764,652	$	8,660	$	250	$	2,264,121
Other Benefits:
Assets:
Cash and cash equivalents
Fixed Income Securities:
Corporate	$	—	$	153,888	$	—	$	—	$	153,888
U.S. Treasury	98,704		—		—		—		98,704
Other (a)	—		27,936		—		—		27,936
Equities:
U.S. Companies	252,181		—		—		—		252,181
International Companies	20,892		—		—		—		20,892
Common and collective trusts:
U.S. Equities	—		80,751		—		—		80,751
International Equities	—		92,382		—		—		92,382
Real Estate	—		10,761		—		—		10,761
Short-term investments and other	—		8,414		—		2,430		10,844
Total Other Benefits	$	371,777	$	374,132	$	—	$	2,430	$	748,339

(a) This category consists primarily of debt securities issued by municipalities.

(b) Represents plan receivables and payables.

The following table shows the changes in fair value for assets that are measured at fair value on a recurring basis using significant unobservable inputs (Level 3) for the year ended December 31, 2014 and 2013 (dollars in thousands):

	Pension
Partnerships	2014			2013
Beginning balance at January 1	$	8,660		$	2,419
Actual return on assets still held at December 31	927			(498		)
Purchases	19,984			7,377
Sales	(1,642		)	(638		)
Transfers in and/or out of Level 3	—			—
Ending balance at December 31	$	27,929		$	8,660

Schedule of estimated future benefit payments, which reflect estimated future employee service, for the next five years and the succeeding five years thereafter

Benefit payments, which reflect estimated future employee service, for the next five years and the succeeding five years thereafter, are estimated to be as follows (dollars in thousands):

Year	Pension		Other Benefits
2015	$	139,013	$	25,134
2016	155,968		27,311
2017	160,080		29,253
2018	167,600		31,258
2019	177,470		33,190
Years 2020-2024	983,557		184,772