Benefit Plans and Other Postretirement Benefits (Tables)

12 Months Ended

Dec. 31, 2018

Benefit Plans and Other Postretirement Benefits [Abstract]

Target Asset Allocations and Plan Assets Measured at Fair Value

The following presents, for each of the fair value hierarchy levels, SPS’ pension plan assets measured at fair value:

	Dec. 31, 2018												Dec. 31, 2017
(Millions of Dollars)	Level 1		Level 2		Level 3		Measured at NAV			Total			Level 1			Level 2		Level 3		Measured at NAV		Total
Cash equivalents	$	21.6	$	—	$	—	$	—		$	21.6		26.9			—		—		—		$	26.9
Commingled funds:	128.6		—		—		132.5			261.1			145.7			—		—		142.7		288.4
Debt securities:	—		98.1		—		—			98.1			—			105.3		—		—		105.3
Equity securities:	14.4		—		—		—			14.4			15.2			—		—		—		15.2
Other	0.2		0.8		—		(4.0		)	(3.0		)	(3.3		)	0.6		—		0.1		(2.6		)
Total	$	164.8	$	98.9	$	—	$	128.5		$	392.2		$	184.5		$	105.9	$	—	$	142.8	$	433.2

The following presents, for each of the fair value hierarchy levels, SPS’ proportionate allocation of the total postretirement benefit plan assets that were measured at fair value:

	Dec. 31, 2018 (a)										Dec. 31, 2017 (a)
(Millions of Dollars)	Level 1		Level 2		Level 3		Measured at NAV		Total		Level 1		Level 2		Level 3		Measured at NAV		Total
Cash equivalents	$	1.8	$	—	$	—	$	—	$	1.8	$	2.8	$	—	$	—	$	—	$	2.8
Insurance contracts	—		4.3		—		—		4.3		—		4.7		—		—		4.7
Commingled funds:	12.8		—		—		3.8		16.6		14.1		—		—		—		14.1
Debt securities:	—		17.2		—		—		17.2		—		19.0		—		—		19.0
Equity securities:	—		—		—		—		—		3.3		—		—		—		3.3
Other	—		0.1		—		—		0.1		—		0.2		—		—		0.2
Total	$	14.6	$	21.6	$	—	$	3.8	$	40.0	$	20.2	$	23.9	$	—	$	—	$	44.1

^(a)  See Note 8 for further information on fair value measurement inputs and methods.

Target asset allocations:

	Pension Benefits				Postretirement Benefits
	2018		2017		2018		2017
Domestic and international equity securities	35	%	34	%	18	%	24	%
Long-duration fixed income securities	32		31		—		—
Short-to-intermediate fixed income securities	16		19		70		60
Alternative investments	15		14		8		9
Cash	2		2		4		7
Total	100	%	100	%	100	%	100	%

Funded Status of Plans

Funded Status — Comparisons of the actuarially computed benefit obligation, changes in plan assets and funded status of the pension and postretirement health care plans for Xcel Energy are presented in the following table:

	Pension Benefits						Postretirement Benefits
(Millions of Dollars)	2018			2017			2018			2017
Change in Benefit Obligation:
Obligation at Jan. 1	$	515.9		$	483.6		$	47.0		$	41.9
Service cost	9.7			9.8			1.1			0.9
Interest cost	18.4			19.7			1.6			1.7
Plan amendments	—			(1.0		)	—			—
Actuarial (gain) loss	(34.8		)	31.2			(5.1		)	4.7
Plan participants’ contributions	—			—			0.6			0.6
Benefit payments (a)	(31.4		)	(27.4		)	(3.4		)	(2.8		)
Obligation at Dec. 31	$	477.8		$	515.9		$	41.8		$	47.0
Change in Fair Value of Plan Assets:
Fair value of plan assets at Jan. 1	$	433.2		$	380.4		$	44.1		$	42.3
Actual return on plan assets	(17.6		)	56.7			(1.3		)	3.8
Employer contributions	8.0			23.5			—			0.2
Plan participants’ contributions	—			—			0.6			0.6
Benefit payments	(31.4		)	(27.4		)	(3.4		)	(2.8		)
Fair value of plan assets at Dec. 31	$	392.2		$	433.2		$	40.0		$	44.1
Funded status of plans at Dec. 31	$	(85.6	)	$	(82.7	)	$	(1.8	)	$	(2.9	)
Amounts recognized in the Balance Sheet at Dec. 31:
Noncurrent liabilities	(85.6		)	(82.7		)	(1.8		)	(2.9		)
Net amounts recognized	$	(85.6	)	$	(82.7	)	$	(1.8	)	$	(2.9	)
Significant Assumptions Used to Measure Benefit Obligations:
Discount rate for year-end valuation	4.31		%	3.63		%	4.32		%	3.62		%
Expected average long-term increase in compensation level	3.75			3.75			N/A			N/A
Mortality table	RP-2014			RP-2014			RP-2014			RP-2014
Health care costs trend rate — initial: Pre-65	N/A			N/A			6.50		%	7.00		%
Health care costs trend rate — initial: Post-65	N/A			N/A			5.30		%	5.50		%
Ultimate trend assumption — initial: Pre-65	N/A			N/A			4.50		%	4.50		%
Ultimate trend assumption — initial: Post-65	N/A			N/A			4.50		%	4.50		%
Years until ultimate trend is reached	N/A			N/A			4			5

^(a)  Includes approximately $6.9 million in 2018 and $0 million in 2017, of lump-sum benefit payments used in the determination of a settlement charge.

Accumulated benefit obligation for the pension plan was $445.8 million and $478.8 million as of Dec. 31, 2018 and 2017, respectively.

Components of Net Periodic Benefit Costs

Components of net periodic benefit cost (credit) and the amounts recognized in other comprehensive income and regulatory assets and liabilities are as follows:

	Pension Benefits									Postretirement Benefits
(Millions of Dollars)	2018			2017			2016			2018			2017			2016
Service cost	$	9.7		$	9.8		$	9.8		$	1.1		$	0.9		$	0.8
Interest cost	18.4			19.7			21.2			1.6			1.7			1.8
Expected return on plan assets	(28.3		)	(27.9		)	(27.6		)	(2.5		)	(2.4		)	(2.4		)
Amortization of prior service credit	(0.1		)	—			—			(0.4		)	(0.4		)	(0.4		)
Amortization of net loss	14.1			13.0			12.0			(0.4		)	(0.6		)	(0.6		)
Settlement charge (a)	3.2			—			—			—			—			—
Net periodic pension cost (credit)	17.0			14.6			15.4			(0.6		)	(0.8		)	(0.8		)
Costs not recognized due to effects of regulation	(2.2		)	0.3			2.0			—			—			—
Net benefit cost (credit) recognized for financial reporting	$	14.8		$	14.9		$	17.4		$	(0.6	)	$	(0.8	)	$	(0.8	)
Significant Assumptions Used to Measure Costs:
Discount rate	3.63		%	4.13		%	4.66		%	3.62		%	4.13		%	4.65		%
Expected average long-term increase in compensation level	3.75			3.75			4.00			—			—			—
Expected average long-term rate of return on assets	6.78			6.78			6.78			5.80			5.80			5.80

^(a)  A settlement charge is required when the amount of all lump-sum distributions during the year is greater than the sum of the service and interest cost components of the annual net periodic pension cost. In 2018, as a result of lump-sum distributions during the 2018 plan year, SPS recorded a total pension settlement charge of $3.3 million the majority of which $0 million was not recognized due to the effects of regulation.

Projected Benefit Payments for the Pension and Postretirement Benefit Plans

Projected Benefit Payments

SPS’ projected benefit payments:

(Millions 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
2019	29.7	3.2	—	3.2
2020	30.0	3.1	—	3.1
2021	29.3	3.2	—	3.2
2022	30.8	3.2	—	3.2
2023	30.8	3.2	—	3.2
2024-2028	156.2	14.4	0.2	14.2

Other Postretirement Benefits Plan [Member]

Benefit Plans and Other Postretirement Benefits [Abstract]

Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost

	Pension Benefits						Postretirement Benefits
(Millions of Dollars)	2018			2017			2018			2017
Amounts Not Yet Recognized as Components of Net Periodic Benefit Cost:
Net loss	$	230.9		$	237.0		$	(9.6	)	$	(8.6	)
Prior service credit	(1.2		)	(1.3		)	(1.8		)	(2.2		)
Total	$	229.7		$	235.7		$	(11.4	)	$	(10.8	)
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	$	12.9		$	13.9		$	—		$	—
Noncurrent regulatory assets	216.8			221.8			—			—
Current regulatory liabilities	—			—			(0.9		)	(0.8		)
Noncurrent regulatory liabilities	—			—			(10.5		)	(10.0		)
Total	$	229.7		$	235.7		$	(11.4	)	$	(10.8	)

Measurement date Dec. 31, 2018 Dec. 31, 2017 Dec. 31, 2018 Dec. 31, 2017