Benefit Plans and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2016

Benefit Plans and Other Postretirement Benefits [Abstract]

Projected Benefit Payments for the Pension and Postretirement Benefit Plans

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
2017	$	28,596	$	3,420	$	24	$	3,396
2018	28,086		3,203		26		3,177
2019	28,545		3,008		24		2,984
2020	29,567		3,015		25		2,990
2021	29,716		3,096		26		3,070
2022-2026	156,673		14,135		148		13,987

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:

	2016		2015
Domestic and international equity securities	36	%	36	%
Long-duration fixed income and interest rate swap securities	31		31
Short-to-intermediate fixed income securities	15		12
Alternative investments	16		19
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, 2016 and 2015:

	Dec. 31, 2016
(Thousands of Dollars)	Level 1		Level 2			Level 3		Investments Measured at NAV (a)		Total
Cash equivalents	$	29,237	$	—		$	—	$	—	$	29,237
Commingled funds:
U.S. equity funds	—		—			—		62,899		62,899
Non U.S. equity funds	—		—			—		46,403		46,403
U.S. corporate bond funds	—		—			—		41,226		41,226
Emerging market equity funds	—		—			—		24,637		24,637
Emerging market debt funds	—		—			—		20,399		20,399
Commodity funds	—		—			—		2,876		2,876
Private equity investments	—		—			—		12,098		12,098
Real estate	—		—			—		23,232		23,232
Other commingled funds	—		—			—		28,247		28,247
Debt securities:
Government securities	—		38,105			—		—		38,105
U.S. corporate bonds	—		36,293			—		—		36,293
Non U.S. corporate bonds	—		5,818			—		—		5,818
Mortgage-backed securities	—		821			—		—		821
Asset-backed securities	—		389			—		—		389
Equity securities:
U.S. equities	10,477		—			—		—		10,477
Other	—		(2,762		)	—		—		(2,762		)
Total	$	39,714	$	78,664		$	—	$	262,017	$	380,395

(a) Based on the requirements of ASU No. 2015-07, investments measured at fair value using a NAV methodology have not been classified in the fair value hierarchy. See Note 2 for further information on the adoption of ASU No. 2015-07.

	Dec. 31, 2015
(Thousands of Dollars)	Level 1		Level 2			Level 3		Investments Measured at NAV (a)		Total
Cash equivalents	$	22,999	$	—		$	—	$	—	$	22,999
Derivatives	—		553			—		—		553
Commingled funds:
U.S. equity funds	—		—			—		55,533		55,533
Non U.S. equity funds	—		—			—		53,449		53,449
U.S. corporate bond funds	—		—			—		32,020		32,020
Emerging market equity funds	—		—			—		23,891		23,891
Emerging market debt funds	—		—			—		23,169		23,169
Commodity funds	—		—			—		7,884		7,884
Private equity investments	—		—			—		19,114		19,114
Real estate	—		—			—		27,690		27,690
Other commingled funds	—		—			—		29,793		29,793
Debt securities:
Government securities	—		37,495			—		—		37,495
U.S. corporate bonds	—		28,826			—		—		28,826
Non U.S. corporate bonds	—		4,626			—		—		4,626
Asset-backed securities	—		323			—		—		323
Equity securities:
U.S. equities	13,492		—			—		—		13,492
Other	—		(1,944		)	—		—		(1,944		)
Total	$	36,491	$	69,879		$	—	$	272,543	$	378,913

(a) Based on the requirements of ASU No. 2015-07, investments measured at fair value using a NAV methodology have not been classified in the fair value hierarchy. See Note 2 for further information on the adoption of ASU No. 2015-07.

Change in Projected Benefit Obligation

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

(Thousands of Dollars)	2016			2015
Accumulated Benefit Obligation at Dec. 31	$	453,317		$	429,726
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	467,394		$	500,690
Service cost	9,761			11,006
Interest cost	21,259			20,184
Actuarial loss (gain)	25,053			(35,154		)
Transfer to other plan	(3,305		)	(2,843		)
Benefit payments	(36,561		)	(26,489		)
Obligation at Dec. 31	$	483,601		$	467,394

Change in Fair Value of Plan Assets

(Thousands of Dollars)	2016			2015
Change in Fair Value of Plan Assets:
Fair value of plan assets at Jan. 1	$	378,913		$	402,269
Actual return (loss) on plan assets	23,306			(6,013		)
Employer contributions	18,088			11,651
Transfer to other plan	(3,351		)	(2,505		)
Benefit payments	(36,561		)	(26,489		)
Fair value of plan assets at Dec. 31	$	380,395		$	378,913

Funded Status of Plans

(Thousands of Dollars)	2016			2015
Funded Status of Plans at Dec. 31:
Funded status (a)	$	(103,206	)	$	(88,481	)

^(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)	2016		2015
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost:
Net loss	$	247,381	$	236,107

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)	2016		2015
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	$	13,524	$	13,690
Noncurrent regulatory assets	233,857		222,417
Total	$	247,381	$	236,107

Schedule of Assumptions Used

	2016		2015		2014
Significant Assumptions Used to Measure Costs:
Discount rate	4.66	%	4.11	%	4.75	%
Expected average long-term increase in compensation level	4.00		3.75		3.75
Expected average long-term rate of return on assets	6.78		7.22		6.90

Measurement date Dec. 31, 2016 Dec. 31, 2015

	2016		2015
Significant Assumptions Used to Measure Benefit Obligations:
Discount rate for year-end valuation	4.13	%	4.66	%
Expected average long-term increase in compensation level	3.75		4.00
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)	2016			2015			2014
Service cost	$	9,761		$	11,006		$	9,184
Interest cost	21,259			20,184			20,444
Expected return on plan assets	(27,602		)	(28,610		)	(26,179		)
Amortization of prior service cost	—			39			54
Amortization of net loss	11,986			15,087			13,326
Net periodic pension cost	15,404			17,706			16,829
Credits not recognized due to effects of regulation	2,042			2,597			3,170
Net benefit cost recognized for financial reporting	$	17,446		$	20,303		$	19,999

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, 2016 and 2015:

	Dec. 31, 2016
(Thousands of Dollars)	Level 1		Level 2		Level 3		Investments Measured at NAV (a)		Total
Cash equivalents	$	1,966	$	—	$	—	$	—	$	1,966
Insurance contracts	—		4,519		—		—		4,519
Commingled funds:
U.S. equity funds	—		—		—		5,208		5,208
U.S fixed income funds	—		—		—		2,593		2,593
Emerging market debt funds	—		—		—		2,911		2,911
Other commingled funds	—		—		—		5,258		5,258
Debt securities:
Government securities	—		3,611		—		—		3,611
U.S. corporate bonds	—		5,962		—		—		5,962
Non U.S. corporate bonds	—		1,653		—		—		1,653
Asset-backed securities	—		1,810		—		—		1,810
Mortgage-backed securities	—		2,748		—		—		2,748
Equity securities:
Non U.S. equities	3,919		—		—		—		3,919
Other	—		139		—		—		139
Total	$	5,885	$	20,442	$	—	$	15,970	$	42,297

^(a)  Based on the requirements of ASU No. 2015-07, investments measured at fair value using a NAV methodology have not been classified in the fair value hierarchy. See Note 2 for further information on the adoption of ASU No. 2015-07.

	Dec. 31, 2015
(Thousands of Dollars)	Level 1		Level 2			Level 3		Investments Measured at NAV (a)		Total
Cash equivalents	$	1,873	$	—		$	—	$	—	$	1,873
Insurance contracts	—		4,501			—		—		4,501
Commingled funds:
U.S. equity funds	—		—			—		3,643		3,643
Non U.S. equity funds	—		—			—		3,204		3,204
U.S fixed income funds	—		—			—		2,311		2,311
Emerging market equity funds	—		—			—		1,058		1,058
Emerging market debt funds	—		—			—		3,401		3,401
Other commingled funds	—		—			—		5,910		5,910
Debt securities:
Government securities	—		3,742			—		—		3,742
U.S. corporate bonds	—		5,710			—		—		5,710
Non U.S. corporate bonds	—		1,239			—		—		1,239
Asset-backed securities	—		2,736			—		—		2,736
Mortgage-backed securities	—		3,396			—		—		3,396
Other	—		(40		)	—		—		(40		)
Total	$	1,873	$	21,284		$	—	$	19,527	$	42,684

^(a)  Based on the requirements of ASU No. 2015-07, investments measured at fair value using a NAV methodology have not been classified in the fair value hierarchy. See Note 2 for further information on the adoption of ASU No. 2015-07.

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

	2016		2015
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	%

Change in Projected Benefit Obligation

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

(Thousands of Dollars)	2016			2015
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	40,864		$	44,342
Service cost	775			954
Interest cost	1,821			1,745
Medicare subsidy reimbursements	31			45
Plan participants’ contributions	653			687
Actuarial loss (gain)	1,293			(3,793		)
Benefit payments	(3,577		)	(3,116		)
Obligation at Dec. 31	$	41,860		$	40,864

Change in Fair Value of Plan Assets

(Thousands of Dollars)	2016			2015
Change in Fair Value of Plan Assets:
Fair value of plan assets at Jan. 1	$	42,684		$	45,356
Actual return (loss) on plan assets	1,978			(421		)
Plan participants’ contributions	653			687
Employer contributions	559			178
Benefit payments	(3,577		)	(3,116		)
Fair value of plan assets at Dec. 31	$	42,297		$	42,684

Funded Status of Plans

(Thousands of Dollars)	2016		2015
Funded Status of Plans at Dec. 31:
Funded status (a)	$	437	$	1,820

^(a)  Amounts are recognized in noncurrent assets on SPS’ balance sheet as of Dec. 31, 2016 and 2015.

Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost

(Thousands of Dollars)	2016			2015
Amounts Not Yet Recognized as Components of Net Periodic Benefit Credit:
Net gain	$	(12,595	)	$	(14,870	)
Prior service credit	(2,630		)	(3,031		)
Total	$	(15,225	)	$	(17,901	)

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)	2016			2015
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	$	(1,004	)	$	(985	)
Noncurrent regulatory liabilities	(14,221		)	(16,916		)
Total	$	(15,225	)	$	(17,901	)

Schedule of Assumptions Used

	2016		2015		2014
Significant Assumptions Used to Measure Costs:
Discount rate	4.65	%	4.08	%	4.82	%
Expected average long-term rate of return on assets	5.80		5.80		7.20

Measurement date Dec. 31, 2016 Dec. 31, 2015

	2016		2015
Significant Assumptions Used to Measure Benefit Obligations:
Discount rate for year-end valuation	4.13	%	4.65	%
Mortality table	RP 2014		RP 2014
Health care costs trend rate — initial	5.50	%	6.00	%

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	$	3,979	$	(3,389	)
Service and interest components	273		(231		)

Components of Net Periodic Benefit Costs

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

(Thousands of Dollars)	2016			2015			2014
Service cost	$	775		$	954		$	1,246
Interest cost	1,821			1,745			2,572
Expected return on plan assets	(2,377		)	(2,540		)	(3,247		)
Amortization of prior service credit	(401		)	(401		)	(401		)
Amortization of net gain	(583		)	(639		)	(321		)
Net periodic postretirement benefit credit	$	(765	)	$	(881	)	$	(151	)