Benefit Plans and Other Postretirement Benefits (Details) - USD ($) $ in Millions		1 Months Ended	3 Months Ended		9 Months Ended
		Jan. 31, 2023	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Pension Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			$ 2	$ 2	$ 5	$ 7
Interest cost (a)	[1]		5	4	17	12
Expected return on plan assets (a)	[1]		(8)	(8)	(24)	(23)
Amortization of net loss (gain) (a)	[1]			3	1	8
Net periodic benefit cost (credit)			(1)	3	(1)	6
Contributions to pension plans		$ 0
Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation			1	(1)	3	(1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			0	2	2	5
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]		0	2	0	2
Amortization of prior service credit (a)	[1]		0
Pension Plan [Member] | Xcel Energy Inc.
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Contributions to pension plans		$ 50
Other Postretirement Benefits Plan [Member]
Components of Net Periodic Benefit Cost (Credit) [Abstract]
Service cost			0	0	0	0
Interest cost (a)	[1]		0	0	1	1
Expected return on plan assets (a)	[1]		0	0	(1)	(1)
Amortization of net loss (gain) (a)	[1]		0	(1)	0	(1)
Net periodic benefit cost (credit)			0	(1)	0	(1)
Defined Benefit Plan Credits Not Recognized Due To Effects of Regulation			0	0	0	0
Defined Benefit Plan, Net Periodic Benefit Cost (Credit)			0	(1)	0	(1)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Gain (Loss) Due to Settlement	[2]		$ 0	$ 0	$ 0	$ 0

[1] The components of net periodic cost other than the service cost component are included in the line item “Other expense, 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 of 2022, 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 rate making.