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 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
2017	$	79,506	$	33,912	$	2,140	$	31,772
2018	78,738		33,652		2,266		31,386
2019	80,914		33,467		2,383		31,084
2020	81,095		33,991		2,475		31,516
2021	82,084		33,588		2,574		31,014
2022-2026	417,876		156,773		14,246		142,527

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 PSCo 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		32
Short-to-intermediate fixed income securities	15		12
Alternative investments	16		18
Cash	2		2
Total	100	%	100	%

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, 2016 and 2015:

	Dec. 31, 2016
(Thousands of Dollars)	Level 1		Level 2			Level 3		Investments Measured at NAV (a)		Total
Cash equivalents	$	34,957	$	—		$	—	$	—	$	34,957
Commingled funds:
U.S. equity funds	—		—			—		165,621		165,621
Non U.S. equity funds	—		—			—		122,197		122,197
U.S. corporate bond funds	—		—			—		96,995		96,995
Emerging market equity funds	—		—			—		64,784		64,784
Emerging market debt funds	—		—			—		53,703		53,703
Commodity funds	—		—			—		7,497		7,497
Private equity investments	—		—			—		31,828		31,828
Real estate	—		—			—		61,048		61,048
Other commingled funds	—		—			—		74,696		74,696
Debt securities:
Government securities	—		168,014			—		—		168,014
U.S. corporate bonds	—		86,081			—		—		86,081
Non U.S. corporate bonds	—		13,828			—		—		13,828
Mortgage-backed securities	—		2,179			—		—		2,179
Asset-backed securities	—		1,032			—		—		1,032
Equity securities:
U.S. equities	27,348		—			—		—		27,348
Other	—		(7,595		)	—		—		(7,595		)
Total	$	62,305	$	263,539		$	—	$	678,369	$	1,004,213

^(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	$	81,954	$	—		$	—	$	—	$	81,954
Derivatives	—		1,204			—		—		1,204
Commingled funds:
U.S. equity funds	—		—			—		125,011		125,011
Non U.S. equity funds	—		—			—		119,394		119,394
U.S. corporate bond funds	—		—			—		82,827		82,827
Emerging market equity funds	—		—			—		56,525		56,525
Emerging market debt funds	—		—			—		54,362		54,362
Commodity funds	—		—			—		14,169		14,169
Private equity investments	—		—			—		34,353		34,353
Real estate	—		—			—		67,075		67,075
Other commingled funds	—		—			—		72,327		72,327
Debt securities:
Government securities	—		214,341			—		—		214,341
U.S. corporate bonds	—		74,787			—		—		74,787
Non U.S. corporate bonds	—		12,127			—		—		12,127
Asset-backed securities	—		881			—		—		881
Equity securities:
U.S. equities	28,797		—			—		—		28,797
Other	—		(3,453		)	—		—		(3,453		)
Total	$	110,751	$	299,887		$	—	$	626,043	$	1,036,681

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)	2016			2015
Accumulated Benefit Obligation at Dec. 31	$	1,213,890		$	1,192,798
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	1,224,650		$	1,277,957
Service cost	25,926			28,260
Interest cost	55,405			50,857
Transfer to other plan	(9,149		)	(2,938		)
Plan amendments	206			—
Actuarial loss (gain)	51,779			(54,737		)
Benefit payments	(96,995		)	(74,749		)
Obligation at Dec. 31	$	1,251,822		$	1,224,650

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	$	1,036,681		$	1,103,865
Actual return (loss) on plan assets	56,762			(9,122		)
Employer contributions	16,829			20,056
Transfer to other plan	(9,064		)	(3,369		)
Benefit payments	(96,995		)	(74,749		)
Fair value of plan assets at Dec. 31	$	1,004,213		$	1,036,681

Funded Status of Plans

(Thousands of Dollars)	2016			2015
Funded Status of Plans at Dec. 31:
Funded status (a)	$	(247,609	)	$	(187,969	)

^(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)	2016			2015
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost:
Net loss	$	554,999		$	521,703
Prior service credit	(12,155		)	(15,572		)
Total	$	542,844		$	506,131

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	$	515,708	$	28,852
Noncurrent regulatory assets	26,853		477,279
Deferred income taxes	108		—
Net-of-tax accumulated OCI	175		—
Total	$	542,844	$	506,131

Schedule of Assumptions Used

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

	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	6.84		6.81		6.81

Components of Net Periodic Benefit Costs

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

(Thousands of Dollars)	2016			2015			2014
Service cost	$	25,926		$	28,260		$	23,939
Interest cost	55,405			50,857			53,277
Expected return on plan assets	(70,769		)	(72,590		)	(70,709		)
Amortization of prior service credit	(3,211		)	(3,136		)	(3,092		)
Amortization of net loss	26,771			36,377			33,892
Net periodic pension cost	34,122			39,768			37,307
Credits (costs) not recognized due to effects of regulation	3,364			(1,464		)	—
Net benefit cost recognized for financial reporting	$	37,486		$	38,304		$	37,307

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, 2016 and 2015:

	Dec. 31, 2016
(Thousands of Dollars)	Level 1		Level 2		Level 3		Investments Measured at NAV (a)		Total
Cash equivalents	$	18,288	$	—	$	—	$	—	$	18,288
Insurance contracts	—		42,046		—		—		42,046
Commingled funds:
U.S. equity funds	—		—		—		48,462		48,462
U.S fixed income funds	—		—		—		24,132		24,132
Emerging market debt funds	—		—		—		27,089		27,089
Other commingled funds	—		—		—		48,922		48,922
Debt securities:
Government securities	—		33,600		—		—		33,600
U.S. corporate bonds	—		55,473		—		—		55,473
Non U.S. corporate bonds	—		15,384		—		—		15,384
Asset-backed securities	—		16,845		—		—		16,845
Mortgage-backed securities	—		25,563		—		—		25,563
Equity securities:
Non U.S. equities	36,462		—		—		—		36,462
Other	—		1,289		—		—		1,289
Total	$	54,750	$	190,200	$	—	$	148,605	$	393,555

^(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	$	17,524	$	—		$	—	$	—	$	17,524
Insurance contracts	—		42,123			—		—		42,123
Commingled funds:
U.S. equity funds	—		—			—		34,089		34,089
Non U.S. equity funds	—		—			—		29,979		29,979
U.S fixed income funds	—		—			—		21,638		21,638
Emerging market equity funds	—		—			—		9,901		9,901
Emerging market debt funds	—		—			—		31,827		31,827
Other commingled funds	—		—			—		55,302		55,302
Debt securities:
Government securities	—		35,016			—		—		35,016
U.S. corporate bonds	—		53,433			—		—		53,433
Non U.S. corporate bonds	—		11,598			—		—		11,598
Asset-backed securities	—		25,602			—		—		25,602
Mortgage-backed securities	—		31,778			—		—		31,778
Other	—		(368		)	—		—		(368		)
Total	$	17,524	$	199,182		$	—	$	182,736	$	399,442

^(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 PSCo 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 PSCo is presented in the following table:

(Thousands of Dollars)	2016			2015
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	403,574		$	443,753
Service cost	768			928
Interest cost	18,070			17,498
Medicare subsidy reimbursements	1,901			1,712
Plan participants’ contributions	5,376			4,961
Actuarial loss (gain)	27,355			(32,001		)
Benefit payments	(35,221		)	(33,277		)
Obligation at Dec. 31	$	421,823		$	403,574

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	$	399,442		$	425,282
Actual return (loss) on plan assets	18,590			(3,076		)
Plan participants’ contributions	5,376			4,961
Employer contributions	5,368			5,552
Benefit payments	(35,221		)	(33,277		)
Fair value of plan assets at Dec. 31	$	393,555		$	399,442

Funded Status of Plans

(Thousands of Dollars)	2016			2015
Funded Status at Dec. 31:
Funded status (a)	$	(28,268	)	$	(4,132	)

^(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)	2016			2015
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost:
Net loss	$	78,359		$	49,226
Prior service credit	(27,695		)	(33,942		)
Total	$	50,664		$	15,284

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:
Noncurrent regulatory assets	$	50,664	$	15,284

Schedule of Assumptions Used

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	%

	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		7.18

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	$	40,100	$	(34,155	)
Service and interest components	1,980		(1,677		)

Components of Net Periodic Benefit Costs

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

(Thousands of Dollars)	2016			2015			2014
Service cost	$	768		$	928		$	1,915
Interest cost	18,070			17,498			23,704
Expected return on plan assets	(22,299		)	(23,803		)	(30,214		)
Amortization of prior service credit	(6,247		)	(6,247		)	(6,247		)
Amortization of net loss	1,931			2,475			6,434
Net periodic postretirement benefit credit	$	(7,777	)	$	(9,149	)	$	(4,408	)