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

The following table lists PSCo’s 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	$	77,898	$	32,197	$	2,234	$	29,963
2017	77,952		32,356		2,373		29,983
2018	80,583		32,381		2,517		29,864
2019	82,760		32,402		2,647		29,755
2020	83,372		33,093		2,753		30,340
2021-2025	430,762		158,040		15,450		142,590

Pension Plans

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, PSCo’s 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	$	81,954	$	—		$	—	$	81,954
Derivatives	—		1,204			—		1,204
Government securities	—		214,341			—		214,341
Corporate bonds	—		86,914			—		86,914
Asset-backed securities	—		881			—		881
Common stock	28,797		—			—		28,797
Private equity investments	—		—			34,353		34,353
Commingled funds	—		573,009			—		573,009
Real estate	—		—			18,681		18,681
Other	—		(3,453		)	—		(3,453		)
Total	$	110,751	$	872,896		$	53,034	$	1,036,681

	Dec. 31, 2014
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents	$	82,486	$	—		$	—	$	82,486
Derivatives	—		508			—		508
Government securities	—		180,912			—		180,912
Corporate bonds	—		115,593			—		115,593
Asset-backed securities	—		1,360			—		1,360
Mortgage-backed securities	—		3,997			—		3,997
Common stock	37,067		—			—		37,067
Private equity investments	—		—			50,210		50,210
Commingled funds	—		629,439			—		629,439
Real estate	—		—			18,410		18,410
Securities lending collateral obligation and other	—		(16,117		)	—		(16,117		)
Total	$	119,553	$	915,692		$	68,620	$	1,103,865

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

	2015		2014
Domestic and international equity securities	36	%	32	%
Long-duration fixed income and interest rate swap securities	32		35
Short-to-intermediate fixed income securities	12		12
Alternative investments	18		18
Cash	2		3
Total	100	%	100	%

Changes in Level 3 Plan Assets

The following tables present the changes in PSCo’s 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	$	50,210	$	7,636	$	(20,036	)	$	(3,457	)	$	—	$	34,353
Real estate	18,410		1,925		(2,371		)	717			—		18,681
Total	$	68,620	$	9,561	$	(22,407	)	$	(2,740	)	$	—	$	53,034

(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	$	49,022	$	8,495	$	(4,299	)	$	(3,008	)	$	—	$	50,210
Real estate	15,556		1,180		(302		)	1,976			—		18,410
Total	$	64,578	$	9,675	$	(4,601	)	$	(1,032	)	$	—	$	68,620

(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	$	4,604	$	—		$	—		$	—		$	(4,604	)	$	—
Mortgage-backed securities	12,058		—			—			—			(12,058		)	—
Private equity investments	47,056		7,074			(4,027		)	(1,081		)	—			49,022
Real estate	19,273		(870		)	3,769			3,048			(9,664		)	15,556
Total	$	82,991	$	6,204		$	(258	)	$	1,967		$	(26,326	)	$	64,578

^(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 PSCo is presented in the following table:

(Thousands of Dollars)	2015			2014
Accumulated Benefit Obligation at Dec. 31	$	1,192,798		$	1,249,739
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	1,277,957		$	1,152,836
Service cost	28,260			23,939
Interest cost	50,857			53,277
Transfer to other plan	(2,938		)	(13,404		)
Actuarial (gain) loss	(54,737		)	133,215
Benefit payments	(74,749		)	(71,906		)
Obligation at Dec. 31	$	1,224,650		$	1,277,957

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	$	1,103,865		$	1,067,057
Actual (loss) return on plan assets	(9,122		)	84,871
Employer contributions	20,056			35,156
Transfer to other plan	(3,369		)	(11,313		)
Benefit payments	(74,749		)	(71,906		)
Fair value of plan assets at Dec. 31	$	1,036,681		$	1,103,865

Funded Status of Plans

(Thousands of Dollars)	2015			2014
Funded Status of Plans at Dec. 31:
Funded status (a)	$	(187,969	)	$	(174,092	)

^(a)  Amounts are recognized in noncurrent liabilities on PSCo’s consolidated 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	$	521,703		$	530,674
Prior service credit	(15,572		)	(18,708		)
Total	$	506,131		$	511,966

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	$	28,852	$	31,774
Noncurrent regulatory assets	477,279		480,192
Total	$	506,131	$	511,966

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	4.66	%	4.11	%
Expected average long-term increase in compensation level	4.00		3.75
Mortality table	RP 2014		RP 2014

	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	6.81		6.81		6.47

Components of Net Periodic Benefit Costs

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

(Thousands of Dollars)	2015			2014			2013
Service cost	$	28,260		$	23,939		$	25,206
Interest cost	50,857			53,277			46,160
Expected return on plan assets	(72,590		)	(70,709		)	(63,821		)
Amortization of prior service credit	(3,136		)	(3,092		)	(1,064		)
Amortization of net loss	36,377			33,892			43,418
Net periodic pension cost	39,768			37,307			49,899
Costs not recognized due to effects of regulation	(1,464		)	—			—
Net benefit cost recognized for financial reporting	$	38,304		$	37,307		$	49,899

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, PSCo’s 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	$	17,524	$	—		$	—	$	17,524
Government securities	—		35,016			—		35,016
Insurance contracts	—		42,123			—		42,123
Corporate bonds	—		65,031			—		65,031
Asset-backed securities	—		25,602			—		25,602
Mortgage-backed securities	—		31,778			—		31,778
Commingled funds	—		182,736			—		182,736
Other	—		(368		)	—		(368		)
Total	$	17,524	$	381,918		$	—	$	399,442

	Dec. 31, 2014
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents (a)	$	23,566	$	—		$	—	$	23,566
Derivatives	—		166			—		166
Government securities	—		43,494			—		43,494
Insurance contracts	—		45,075			—		45,075
Corporate bonds	—		48,527			—		48,527
Asset-backed securities	—		3,240			—		3,240
Mortgage-backed securities	—		10,071			—		10,071
Commingled funds	—		252,790			—		252,790
Other	—		(1,647		)	—		(1,647		)
Total	$	23,566	$	401,716		$	—	$	425,282

^(a)  Includes restricted cash of $0.9 million at Dec. 31, 2014.

The following table presents the target postretirement asset allocations for Xcel Energy Inc. and PSCo 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 PSCo’s 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	$	670	$	—	$	—	$	—	$	(670	)	$	—
Mortgage-backed securities	35,394		—		—		—		(35,394		)	—
Total	$	36,064	$	—	$	—	$	—	$	(36,064	)	$	—

^(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 PSCo is presented in the following table:

(Thousands of Dollars)	2015			2014
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	443,753		$	508,971
Service cost	928			1,915
Interest cost	17,498			23,704
Medicare subsidy reimbursements	1,712			1,753
Plan participants’ contributions	4,961			4,625
Actuarial gain	(32,001		)	(63,130		)
Benefit payments	(33,277		)	(34,085		)
Obligation at Dec. 31	$	403,574		$	443,753

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	$	425,282		$	438,193
Actual (loss) return on plan assets	(3,076		)	11,060
Plan participants’ contributions	4,961			4,625
Employer contributions	5,552			5,489
Benefit payments	(33,277		)	(34,085		)
Fair value of plan assets at Dec. 31	$	399,442		$	425,282

Funded Status of Plans

(Thousands of Dollars)	2015			2014
Funded Status at Dec. 31:
Funded status (a)	$	(4,132	)	$	(18,471	)

^(a)  Amounts are recognized in noncurrent liabilities on PSCo’s consolidated 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	$	49,226		$	56,823
Prior service credit	(33,942		)	(40,189		)
Total	$	15,284		$	16,634

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:
Noncurrent regulatory assets	$	15,284	$	16,634

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		7.18		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 PSCo:

	One-Percentage Point
(Thousands of Dollars)	Increase		Decrease
APBO	$	38,946	$	(33,136	)
Service and interest components	2,093		(1,743		)

Components of Net Periodic Benefit Costs

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

(Thousands of Dollars)	2015			2014			2013
Service cost	$	928		$	1,915		$	2,564
Interest cost	17,498			23,704			22,210
Expected return on plan assets	(23,803		)	(30,214		)	(29,227		)
Amortization of transition obligation	—			—			785
Amortization of prior service credit	(6,247		)	(6,247		)	(7,666		)
Amortization of net loss	2,475			6,434			13,699
Net periodic postretirement benefit (credit) cost	$	(9,149	)	$	(4,408	)	$	2,365