Benefit Plans and Other Postretirement Benefits, Pension Benefits (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019 USD ($) Plan	Dec. 31, 2018 USD ($) Plan	Dec. 31, 2017 USD ($) Plan
Target Pension Asset Allocations [Abstract]
Defined Contribution Plan, Cost		$ 3.0	$ 3.0	$ 3.0
Pension Plan [Member]
Pension Benefits [Abstract]
Total benefit obligation		518.8	477.8	515.9
Net benefit cost recognized for financial reporting		$ 14.8	$ 14.8	$ 14.9
Minimum number of years historical achieved weighted average annual returns used to determine investment return assumptions (in years)		20 years
Expected average long-term rate of return on assets (as a percent)		6.78%	6.78%	6.78%
Target Pension Asset Allocations [Abstract]
Target pension asset allocations (as a percent)		100.00%	100.00%
Pension Plan [Member] | Domestic and international equity securities
Target Pension Asset Allocations [Abstract]
Target pension asset allocations (as a percent)		37.00%	35.00%
Pension Plan [Member] | Long-Duration Fixed Income and Long-duration fixed income and interest rate swap securities
Target Pension Asset Allocations [Abstract]
Target pension asset allocations (as a percent)		30.00%	32.00%
Pension Plan [Member] | Short-to-intermediate fixed income securities
Target Pension Asset Allocations [Abstract]
Target pension asset allocations (as a percent)		14.00%	16.00%
Pension Plan [Member] | Alternative investments
Target Pension Asset Allocations [Abstract]
Target pension asset allocations (as a percent)		17.00%	15.00%
Pension Plan [Member] | Cash
Target Pension Asset Allocations [Abstract]
Target pension asset allocations (as a percent)		2.00%	2.00%
Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan
Pension Benefits [Abstract]
Total benefit obligation		$ 2.0	$ 2.0
Net benefit cost recognized for financial reporting		4.0	4.0
Parent Company [Member]
Target Pension Asset Allocations [Abstract]
Total contributions to Xcel Energy's postretirement health care plans during the year		$ 15.0	$ 11.0	$ 20.0
Parent Company [Member] | Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined benefit plan number of pension plans to which contributions were made | Plan		4	4	4
Parent Company [Member] | Supplemental Executive Retirement Plan (SERP) and Nonqualified Pension Plan
Pension Benefits [Abstract]
Total benefit obligation		$ 39.0	$ 33.0
Forecast [Member] | Pension Plan [Member]
Pension Benefits [Abstract]
Expected average long-term rate of return on assets for next fiscal year (as a percent)	6.78%