Benefit Plans and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2013

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
2014	$	77,490	$	36,778	$	2,396	$	34,382
2015	78,297		38,061		2,564		35,497
2016	80,894		39,418		2,715		36,703
2017	81,037		40,135		2,881		37,254
2018	84,004		42,019		3,042		38,977
2019-2023	430,547		206,729		17,204		189,525

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, 2013 and 2012:

	Dec. 31, 2013
(Thousands of Dollars)	Level 1		Level 2		Level 3		Total
Cash equivalents	$	42,721	$	—	$	—	$	42,721
Derivatives	—		14,755		—		14,755
Government securities	—		125,891		—		125,891
Corporate bonds	—		183,078		—		183,078
Asset-backed securities	—		2,356		—		2,356
Mortgage-backed securities	—		5,267		—		5,267
Common stock	34,742		—		—		34,742
Private equity investments	—		—		49,022		49,022
Commingled funds	—		582,722		—		582,722
Real estate	—		—		15,556		15,556
Securities lending collateral obligation and other	—		10,947		—		10,947
Total	$	77,463	$	925,016	$	64,578	$	1,067,057

	Dec. 31, 2012
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents	$	49,367	$	—		$	—	$	49,367
Derivatives	—		7,190			—		7,190
Government securities	—		159,137			—		159,137
Corporate bonds	—		248,759			—		248,759
Asset-backed securities	—		—			4,604		4,604
Mortgage-backed securities	—		—			12,058		12,058
Common stock	21,560		—			—		21,560
Private equity investments	—		—			47,056		47,056
Commingled funds	—		495,697			—		495,697
Real estate	—		—			19,273		19,273
Securities lending collateral obligation and other	—		(9,393		)	—		(9,393		)
Total	$	70,927	$	901,390		$	82,991	$	1,055,308

The following table presents the target pension asset allocations for PSCo:

	2013		2012
Domestic and international equity securities	29	%	20	%
Long-duration fixed income and interest rate swap securities	36		50
Short-to-intermediate term fixed income securities	14		9
Alternative investments	19		19
Cash	2		2
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, 2013, 2012 and 2011:

(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.

(Thousands of Dollars)	Jan. 1, 2012		Net Realized Gains (Losses)		Net Unrealized Gains (Losses)			Purchases, Issuances and Settlements, Net			Transfers Out of Level 3		Dec. 31, 2012
Asset-backed securities	$	9,824	$	1,175	$	(1,597	)	$	(4,798	)	$	—	$	4,604
Mortgage-backed securities	23,614		550		(625		)	(11,481		)	—		12,058
Private equity investments	49,489		5,206		(7,001		)	(638		)	—		47,056
Real estate	11,230		6		1,843			6,194			—		19,273
Total	$	94,157	$	6,937	$	(7,380	)	$	(10,723	)	$	—	$	82,991

(Thousands of Dollars)	Jan. 1, 2011		Net Realized Gains (Losses)			Net Unrealized Gains (Losses)			Purchases, Issuances, and Settlements, Net			Transfers Out of Level 3		Dec. 31, 2011
Asset-backed securities	$	8,399	$	713		$	(744	)	$	1,456		$	—	$	9,824
Mortgage-backed securities	36,134		320			(1,774		)	(11,066		)	—		23,614
Private equity investments	36,420		1,229			3,925			7,915			—		49,489
Real estate	21,962		(190		)	6,000			(16,542		)	—		11,230
Total	$	102,915	$	2,072		$	7,407		$	(18,237	)	$	—	$	94,157

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)	2013			2012
Accumulated Benefit Obligation at Dec. 31	$	1,134,184		$	1,178,447
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	1,194,371		$	1,047,373
Service cost	25,206			22,719
Interest cost	46,160			51,192
Transfer from other plan	11,306			—
Plan amendments	—			626
Actuarial (gain) loss	(49,384		)	138,259
Benefit payments	(74,823		)	(65,798		)
Obligation at Dec. 31	$	1,152,836		$	1,194,371

Change in Fair Value of Plan Assets

(Thousands of Dollars)	2013			2012
Change in Fair Value of Plan Assets:
Fair value of plan assets at Jan. 1	$	1,055,308		$	969,207
Actual return on plan assets	30,684			110,113
Employer contributions	44,582			41,786
Transfer from other plan	11,306			—
Benefit payments	(74,823		)	(65,798		)
Fair value of plan assets at Dec. 31	$	1,067,057		$	1,055,308

Funded Status of Plans

(Thousands of Dollars)	2013			2012
Funded Status of Plans at Dec. 31:
Funded status (a)	$	(85,779	)	$	(139,063	)

^(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)	2013			2012
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost:
Net loss	$	450,202		$	509,867
Prior service credit	(21,800		)	(22,864		)
Total	$	428,402		$	487,003

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)	2013		2012
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	$	36,271	$	33,177
Noncurrent regulatory assets	392,131		453,826
Total	$	428,402	$	487,003

Schedule of Assumptions Used

	2013		2012		2011
Significant Assumptions Used to Measure Costs:
Discount rate	4.00	%	5.00	%	5.50	%
Expected average long-term increase in compensation level	3.75		4.00		4.00
Expected average long-term rate of return on assets	6.47		6.65		7.00

Measurement date Dec. 31, 2013 Dec. 31, 2012

	2013		2012
Significant Assumptions Used to Measure Benefit Obligations:
Discount rate for year-end valuation	4.75	%	4.00	%
Expected average long-term increase in compensation level	3.75		3.75
Mortality table	RP 2000		RP 2000

Components of Net Periodic Benefit Costs

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

(Thousands of Dollars)	2013			2012			2011
Service cost	$	25,206		$	22,719		$	17,726
Interest cost	46,160			51,192			52,234
Expected return on plan assets	(63,821		)	(65,302		)	(67,946		)
Amortization of prior service (credit) cost	(1,064		)	228			222
Amortization of net loss	43,418			34,332			28,126
Net periodic pension cost	$	49,899		$	43,169		$	30,362

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 postretirement benefit plan assets that are measured at fair value as of Dec. 31, 2013 and 2012:

	Dec 31, 2013
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents	$	18,202	$	—		$	—	$	18,202
Derivatives	—		(370		)	—		(370		)
Government securities	—		52,028			—		52,028
Insurance contracts	—		47,029			—		47,029
Corporate bonds	—		46,186			—		46,186
Asset-backed securities	—		2,991			—		2,991
Mortgage-backed securities	—		21,593			—		21,593
Commingled funds	—		265,620			—		265,620
Other	—		(15,086		)	—		(15,086		)
Total	$	18,202	$	419,991		$	—	$	438,193

	Dec 31, 2012
(Thousands of Dollars)	Level 1		Level 2			Level 3		Total
Cash equivalents	$	80,852	$	—		$	—	$	80,852
Derivatives	—		4			—		4
Government securities	—		65,059			—		65,059
Insurance contracts	—		44,295			—		44,295
Corporate bonds	—		38,806			—		38,806
Asset-backed securities	—		—			670		670
Mortgage-backed securities	—		—			35,394		35,394
Commingled funds	—		202,331			—		202,331
Other	—		(41,494		)	—		(41,494		)
Total	$	80,852	$	309,001		$	36,064	$	425,917

Changes in Level 3 Plan Assets

The following tables present the changes in PSCo’s Level 3 postretirement benefit plan assets for the years ended Dec. 31, 2013, 2012 and 2011:

(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.

(Thousands of Dollars)	Jan. 1, 2012		Net Realized Gains (Losses)			Net Unrealized Gains (Losses)			Purchases, Issuances and Settlements, Net			Transfers Out of Level 3		Dec. 31, 2012
Asset-backed securities	$	6,941	$	(293	)	$	1,669		$	(7,647	)	$	—	$	670
Mortgage-backed securities	24,038		(641		)	3,429			8,568			—		35,394
Private equity investments	479		—			(65		)	(414		)	—		—
Real estate	144		—			35			(179		)	—		—
Total	$	31,602	$	(934	)	$	5,068		$	328		$	—	$	36,064

(Thousands of Dollars)	Jan. 1, 2011		Net Realized Gains (Losses)			Net Unrealized Gains (Losses)			Purchases, Issuances, and Settlements, Net			Transfers Out of Level 3		Dec. 31, 2011
Asset-backed securities	$	2,427	$	(8	)	$	(979	)	$	5,501		$	—	$	6,941
Mortgage-backed securities	17,461		(1,469		)	1,714			6,332			—		24,038
Private equity investments	1,018		12			9			(560		)	—		479
Real estate	614		(2		)	206			(674		)	—		144
Total	$	21,520	$	(1,467	)	$	950		$	10,599		$	—	$	31,602

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)	2013			2012
Change in Projected Benefit Obligation:
Obligation at Jan. 1	$	599,831		$	507,734
Service cost	2,564			2,825
Interest cost	22,210			24,527
Medicare subsidy reimbursements	923			2,185
Plan amendments	(14,571		)	(1,541		)
Plan participants’ contributions	4,589			4,042
Actuarial (gain) loss	(76,889		)	92,694
Benefit payments	(29,686		)	(32,635		)
Obligation at Dec. 31	$	508,971		$	599,831

Change in Fair Value of Plan Assets

(Thousands of Dollars)	2013			2012
Change in Fair Value of Plan Assets:
Fair value of plan assets at Jan. 1	$	425,917		$	376,508
Actual return on plan assets	30,390			50,473
Plan participants’ contributions	4,589			4,042
Employer contributions	6,983			27,529
Benefit payments	(29,686		)	(32,635		)
Fair value of plan assets at Dec. 31	$	438,193		$	425,917

Funded Status of Plans

(Thousands of Dollars)	2013			2012
Funded Status at Dec. 31:
Funded status (a)	$	(70,778	)	$	(173,914	)

^(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)	2013			2012
Amounts Not Yet Recognized as Components of Net Periodic Cost:
Net loss	$	107,232		$	198,983
Prior service credit	(46,436		)	(39,531		)
Transition obligation	—			785
Total	$	60,796		$	160,237

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)	2013		2012
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	$	8,798	$	4,597
Noncurrent regulatory assets	51,998		155,640
Total	$	60,796	$	160,237

Schedule of Assumptions Used

	2013		2012		2011
Significant Assumptions Used to Measure Costs:
Discount rate	4.10	%	5.00	%	5.50	%
Expected average long-term rate of return on assets	7.11		6.75		7.50

Measurement date Dec. 31, 2013 Dec. 31, 2012

	2013		2012
Significant Assumptions Used to Measure Benefit Obligations:
Discount rate for year-end valuation	4.82	%	4.10	%
Mortality table	RP 2000		RP 2000
Health care costs trend rate — initial	7.00	%	7.50	%

Components of Net Periodic Benefit Costs

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

(Thousands of Dollars)	2013			2012			2011
Service cost	$	2,564		$	2,825		$	3,625
Interest cost	22,210			24,527			28,391
Expected return on plan assets	(29,227		)	(25,056		)	(27,961		)
Amortization of transition obligation	785			11,004			11,004
Amortization of prior service credit	(7,666		)	(5,150		)	(2,913		)
Amortization of net loss	13,699			10,930			8,942
Net periodic postretirement benefit cost	$	2,365		$	19,080		$	21,088
Additional cost recognized due to effects of regulation	—			3,891			3,891
Net benefit cost recognized for financial reporting	$	2,365		$	22,971		$	24,979

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	$	52,619	$	(44,089	)
Service and interest components	2,448		(1,933		)