Benefit Plans and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2015

Benefit Plans and Other Postretirement Benefits [Abstract]

Projected Benefit Payments for the Pension and Postretirement Benefit Plans

Projected Benefit Payments — The following table lists SPS’ projected benefit payments for the pension and postretirement benefit plans:

(Thousands of Dollars)	Projected Pension Benefit Payments		Gross Projected Postretirement Health Care Benefit Payments		Expected Medicare Part D Subsidies		Net Projected Postretirement Health Care Benefit Payments
2016	$	27,031	$	3,418	$	24	$	3,394
2017	27,341		3,307		25		3,282
2018	28,230		3,155		29		3,126
2019	29,159		3,036		25		3,011
2020	29,777		3,024		25		2,999
2021-2025	156,982		14,657		153		14,504

Pension Plans

Benefit Plans and Other Postretirement Benefits [Abstract]

Target Asset Allocations and Plan Assets Measured at Fair Value

The following table presents the target pension asset allocations for SPS at Dec. 31 for the upcoming year:

	2015		2014
Domestic and international equity securities	36	%	39	%
Long-duration fixed income and interest rate swap securities	31		23
Short-to-intermediate fixed income securities	12		14
Alternative investments	19		22
Cash	2		2
Total	100	%	100	%

The following tables present, for each of the fair value hierarchy levels, SPS’ pension plan assets that are measured at fair value as of Dec. 31, 2015 and 2014:

	Dec. 31, 2015
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents	$	22,999	$	—		$	—	$	22,999
Derivatives	—		553			—		553
Government securities	—		37,495			—		37,495
Corporate bonds	—		33,452			—		33,452
Asset-backed securities	—		323			—		323
Common stock	13,492		—			—		13,492
Private equity investments	—		—			19,114		19,114
Commingled funds	—		245,717			—		245,717
Real estate	—		—			7,712		7,712
Other	—		(1,944		)	—		(1,944		)
Total	$	36,491	$	315,596		$	26,826	$	378,913

	Dec. 31, 2014
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents	$	17,181	$	—		$	—	$	17,181
Derivatives	—		748			—		748
Government securities	—		68,058			—		68,058
Corporate bonds	—		46,531			—		46,531
Asset-backed securities	—		494			—		494
Mortgage-backed securities	—		1,451			—		1,451
Common stock	13,439		—			—		13,439
Private equity investments	—		—			18,331		18,331
Commingled funds	—		233,232			—		233,232
Real estate	—		—			6,689		6,689
Securities lending collateral obligation and other	—		(3,885		)	—		(3,885		)
Total	$	30,620	$	346,629		$	25,020	$	402,269

Changes in Level 3 Plan Assets

The following tables present the changes in SPS’ Level 3 pension plan assets for the years ended Dec. 31, 2015, 2014 and 2013:

(Thousands of Dollars)	Jan. 1, 2015		Net Realized Gains (Losses)		Net Unrealized Gains (Losses)			Purchases, Issuances and Settlements, Net			Transfers Out of Level 3		Dec. 31, 2015
Private equity investments	$	18,331	$	4,248	$	(1,541	)	$	(1,924	)	$	—	$	19,114
Real estate	6,689		1,071		(447		)	399			—		7,712
Total	$	25,020	$	5,319	$	(1,988	)	$	(1,525	)	$	—	$	26,826

(Thousands of Dollars)	Jan. 1, 2014		Net Realized Gains (Losses)		Net Unrealized Gains (Losses)			Purchases, Issuances and Settlements, Net			Transfers Out of Level 3		Dec. 31, 2014
Private equity investments	$	18,222	$	3,101	$	(1,894	)	$	(1,098	)	$	—	$	18,331
Real estate	5,755		431		(219		)	722			—		6,689
Total	$	23,977	$	3,532	$	(2,113	)	$	(376	)	$	—	$	25,020

(Thousands of Dollars)	Jan. 1, 2013		Net Realized Gains (Losses)			Net Unrealized Gains (Losses)			Purchases, Issuances and Settlements, Net			Transfers Out of Level 3 (a)			Dec. 31, 2013
Asset-backed securities	$	1,755	$	—		$	—		$	—		$	(1,755	)	$	—
Mortgage-backed securities	4,331		—			—			—			(4,331		)	—
Private equity investments	17,049		2,630			(1,055		)	(402		)	—			18,222
Real estate	6,969		(322		)	1,475			1,128			(3,495		)	5,755
Total	$	30,104	$	2,308		$	420		$	726		$	(9,581	)	$	23,977

^(a)  Transfers out of Level 3 into Level 2 were principally due to diminished use of unobservable inputs that were previously significant to these fair value measurements and were subsequently sold during 2013.

Change in Projected Benefit Obligation

Benefit Obligations — A comparison of the actuarially computed pension benefit obligation and plan assets for SPS is presented in the following table:

(Thousands of Dollars)	2015			2014
Accumulated Benefit Obligation at Dec. 31	$	429,726		$	458,793
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	500,690		$	434,307
Service cost	11,006			9,184
Interest cost	20,184			20,444
Actuarial (gain) loss	(35,154		)	63,209
Transfer to other plan	(2,843		)	(1,939		)
Benefit payments	(26,489		)	(24,515		)
Obligation at Dec. 31	$	467,394		$	500,690

Change in Fair Value of Plan Assets

(Thousands of Dollars)	2015			2014
Change in Fair Value of Plan Assets:
Fair value of plan assets at Jan. 1	$	402,269		$	393,393
Actual (loss) return on plan assets	(6,013		)	30,159
Employer contributions	11,651			4,869
Transfer (to) from other plan	(2,505		)	(1,637		)
Benefit payments	(26,489		)	(24,515		)
Fair value of plan assets at Dec. 31	$	378,913		$	402,269

Funded Status of Plans

(Thousands of Dollars)	2015			2014
Funded Status of Plans at Dec. 31:
Funded status (a)	$	(88,481	)	$	(98,421	)

^(a)  Amounts are recognized in noncurrent liabilities on SPS’ balance sheets.

Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost

(Thousands of Dollars)	2015		2014
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost:
Net loss	$	236,107	$	252,063
Prior service cost	—		39
Total	$	236,107	$	252,102

Amounts Not Yet Recognized as Components of Net Periodic Benefit Costs Recorded on the Balance Sheet Based Upon Expected Recovery in Rates

(Thousands of Dollars)	2015		2014
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost Have Been Recorded as Follows Based Upon Expected Recovery in Rates:
Current regulatory assets	$	13,690	$	14,437
Noncurrent regulatory assets	222,417		237,665
Total	$	236,107	$	252,102

Schedule of Assumptions Used

	2015		2014		2013
Significant Assumptions Used to Measure Costs:
Discount rate	4.11	%	4.75	%	4.00	%
Expected average long-term increase in compensation level	3.75		3.75		3.75
Expected average long-term rate of return on assets	7.22		6.90		6.49

Measurement date Dec. 31, 2015 Dec. 31, 2014

	2015		2014
Significant Assumptions Used to Measure Benefit Obligations:
Discount rate for year-end valuation	4.66	%	4.11	%
Expected average long-term increase in compensation level	4.00		3.75
Mortality table	RP 2014		RP 2014

Components of Net Periodic Benefit Costs

Benefit Costs —The components of SPS’ net periodic pension cost were:

(Thousands of Dollars)	2015			2014			2013
Service cost	$	11,006		$	9,184		$	9,615
Interest cost	20,184			20,444			17,908
Expected return on plan assets	(28,610		)	(26,179		)	(23,970		)
Amortization of prior service cost	39			54			870
Amortization of net loss	15,087			13,326			17,148
Net periodic pension cost	17,706			16,829			21,571
Credits (costs) not recognized due to effects of regulation	2,597			3,170			(1,269		)
Net benefit cost recognized for financial reporting	$	20,303		$	19,999		$	20,302

Postretirement Benefit Plan

Benefit Plans and Other Postretirement Benefits [Abstract]

Target Asset Allocations and Plan Assets Measured at Fair Value

The following tables present, for each of the fair value hierarchy levels, SPS’ proportionate allocation of the total postretirement benefit plan assets that are measured at fair value as of Dec. 31, 2015 and 2014:

	Dec. 31, 2015
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents	$	1,873	$	—		$	—	$	1,873
Government securities	—		3,742			—		3,742
Insurance contracts	—		4,501			—		4,501
Corporate bonds	—		6,949			—		6,949
Asset-backed securities	—		2,736			—		2,736
Mortgage-backed securities	—		3,396			—		3,396
Commingled funds	—		19,527			—		19,527
Other	—		(40		)	—		(40		)
Total	$	1,873	$	40,811		$	—	$	42,684

	Dec. 31, 2014
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents (a)	$	2,513	$	—		$	—	$	2,513
Derivatives	—		18			—		18
Government securities	—		4,639			—		4,639
Insurance contracts	—		4,807			—		4,807
Corporate bonds	—		5,175			—		5,175
Asset-backed securities	—		345			—		345
Mortgage-backed securities	—		1,074			—		1,074
Commingled funds	—		26,960			—		26,960
Other	—		(175		)	—		(175		)
Total	$	2,513	$	42,843		$	—	$	45,356

^(a)  Includes restricted cash of $0.1 million at Dec. 31, 2014.

The following table presents the target postretirement asset allocations for Xcel Energy Inc. and SPS at Dec. 31 for the upcoming year:

	2015		2014
Domestic and international equity securities	25	%	25	%
Short-to-intermediate fixed income securities	57		57
Alternative investments	13		13
Cash	5		5
Total	100	%	100	%

Changes in Level 3 Plan Assets

For the years ended Dec. 31, 2015 and 2014, there were no assets transferred in or out of Level 3. The following table presents the changes in SPS’ Level 3 postretirement benefit plan assets for the year ended Dec. 31, 2013:

(Thousands of Dollars)	Jan. 1, 2013		Net Realized Gains (Losses)		Net Unrealized Gains (Losses)		Purchases, Issuances and Settlements, Net		Transfers Out of Level 3 (a)			Dec. 31, 2013
Asset-backed securities	$	73	$	—	$	—	$	—	$	(73	)	$	—
Mortgage-backed securities	3,841		—		—		—		(3,841		)	—
Total	$	3,914	$	—	$	—	$	—	$	(3,914	)	$	—

^(a)  Transfers out of Level 3 into Level 2 were principally due to diminished use of unobservable inputs that were previously significant to these fair value measurements and were subsequently sold during 2013.

Change in Projected Benefit Obligation

Benefit Obligations — A comparison of the actuarially computed benefit obligation and plan assets for SPS is presented in the following table:

(Thousands of Dollars)	2015			2014
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	44,342		$	54,982
Service cost	954			1,246
Interest cost	1,745			2,572
Medicare subsidy reimbursements	45			18
Plan participants’ contributions	687			728
Actuarial gain	(3,793		)	(11,828		)
Benefit payments	(3,116		)	(3,376		)
Obligation at Dec. 31	$	40,864		$	44,342

Change in Fair Value of Plan Assets

(Thousands of Dollars)	2015			2014
Change in Fair Value of Plan Assets:
Fair value of plan assets at Jan. 1	$	45,356		$	46,738
Actual (loss) return on plan assets	(421		)	1,073
Plan participants’ contributions	687			728
Employer contributions	178			193
Benefit payments	(3,116		)	(3,376		)
Fair value of plan assets at Dec. 31	$	42,684		$	45,356

Funded Status of Plans

(Thousands of Dollars)	2015		2014
Funded Status of Plans at Dec. 31:
Funded status (a)	$	1,820	$	1,014

^(a)  Amounts are recognized in noncurrent assets and noncurrent liabilities on SPS’ balance sheet as of Dec. 31, 2015 and 2014, respectively.

Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost

(Thousands of Dollars)	2015			2014
Amounts Not Yet Recognized as Components of Net Periodic Benefit Credit:
Net gain	$	(14,870	)	$	(14,677	)
Prior service credit	(3,031		)	(3,432		)
Total	$	(17,901	)	$	(18,109	)

Amounts Not Yet Recognized as Components of Net Periodic Benefit Costs Recorded on the Balance Sheet Based Upon Expected Recovery in Rates

(Thousands of Dollars)	2015			2014
Amounts Not Yet Recognized as Components of Net Periodic Benefit Credit Have Been Recorded as Follows Based Upon Expected Recovery in Rates:
Current regulatory liabilities	$	(985	)	$	(892	)
Noncurrent regulatory liabilities	(16,916		)	(17,217		)
Total	$	(17,901	)	$	(18,109	)

Schedule of Assumptions Used

Measurement date Dec. 31, 2015 Dec. 31, 2014

	2015		2014
Significant Assumptions Used to Measure Benefit Obligations:
Discount rate for year-end valuation	4.65	%	4.08	%
Mortality table	RP 2014		RP 2014
Health care costs trend rate — initial	6.00	%	6.50	%

	2015		2014		2013
Significant Assumptions Used to Measure Costs:
Discount rate	4.08	%	4.82	%	4.10	%
Expected average long-term rate of return on assets	5.80		7.20		7.11

Effects of One-Percent Change in Assumed Health Care Cost Trend Rate

A one-percent change in the assumed health care cost trend rate would have the following effects on SPS:

	One-Percentage Point
(Thousands of Dollars)	Increase		Decrease
APBO	$	3,944	$	(3,355	)
Service and interest components	307		(255		)

Components of Net Periodic Benefit Costs

Benefit Costs — The components of SPS’ net periodic postretirement benefit costs were:

(Thousands of Dollars)	2015			2014			2013
Service cost	$	954		$	1,246		$	1,368
Interest cost	1,745			2,572			2,352
Expected return on plan assets	(2,540		)	(3,247		)	(3,183		)
Amortization of prior service credit	(401		)	(401		)	(484		)
Amortization of net gain	(639		)	(321		)	(6		)
Net periodic postretirement benefit (credit) cost	$	(881	)	$	(151	)	$	47