Benefit Plans and Other Postretirement Benefits (Details) $ in Millions		1 Months Ended	3 Months Ended			9 Months Ended
		Jan. 31, 2022 USD ($) Plan	Sep. 30, 2022 USD ($)		Sep. 30, 2021 USD ($)	Sep. 30, 2022 USD ($)		Sep. 30, 2021 USD ($)
Pension Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			$ 2		$ 3	$ 7		$ 8
Interest cost (a)	[1]		4		3	12		11
Expected return on plan assets (a)	[1]		(8)		(7)	(23)		(22)
Amortization of net loss (gain) (a)	[1]		3		4	8		11
Net periodic benefit cost (credit)			3		3	6		8
Contributions to pension plans		$ 0
Effects of regulation			(1)		(1)	(1)		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			2		2	5		8
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			2	[2]	0	2	[2]	0
Pension Plan [Member] | Xcel Energy Inc.
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Contributions to pension plans		$ 50
Number of pension plans to which contributions were made | Plan		4
Other Postretirement Benefits Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0		0	0		0
Interest cost (a)			0		0	1	[1]	0
Expected return on plan assets (a)			0		0	(1)	[1]	(1)	[1]
Amortization of net loss (gain) (a)			(1)	[1]	0	(1)	[1]	0
Net periodic benefit cost (credit)			(1)		0	(1)		(1)
Effects of regulation			0		0	0		0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			(1)		0	(1)		(1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement			$ 0		$ 0	$ 0		$ 0

[1] The components of net periodic cost other than the service cost component are included in the line item “Other income, net” in the statements of income or capitalized on the balance sheets as a regulatory asset.

[2] 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 the third quarter as a result of lump-sum distributions during the 2022 plan year, SPS recorded a pension settlement charge of $2 million, the majority of which was not recognized in earnings due to the effects of regulation.