Benefit Plans and Other Postretirement Benefits (Details) $ in Millions		1 Months Ended	3 Months Ended
		Jan. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2019 USD ($)	Jan. 31, 2019 Plan
Pension Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost			$ 24	$ 22
Interest cost	[1]		31	36
Expected return on plan assets	[1]		(52)	(51)
Amortization of prior service credit	[1]		(1)	(1)
Amortization of net loss	[1]		25	22
Net periodic benefit cost (credit)			27	28
Credits not recognized due to effects of regulation			2	1
Net benefit cost (credit) recognized for financial reporting			29	29
Pension Plan [Member] | Parent Company
Components of Net Periodic Benefit Cost [Abstract]
Contributions to Xcel Energy's pension plans		$ 150
Number of pension plans to which contributions were made | Plan					4
Other Postretirement Benefits Plan [Member]
Components of Net Periodic Benefit Cost [Abstract]
Service cost			0	0
Interest cost	[1]		5	6
Expected return on plan assets	[1]		(5)	(5)
Amortization of prior service credit	[1]		(2)	(3)
Amortization of net loss	[1]		1	1
Net periodic benefit cost (credit)			(1)	(1)
Credits not recognized due to effects of regulation			1	0
Net benefit cost (credit) recognized for financial reporting			$ 0	$ (1)

[1] Components of net periodic cost other than the service cost component are included in the line item “other (expense) income, net” in the consolidated statement of income or capitalized on the consolidated balance sheet as a regulatory asset.