Letters of Credit (Details) - USD ($) $ in Millions	Sep. 30, 2026	Dec. 31, 2025
Line of Credit Facility [Abstract]
Amount outstanding at period end	$ 3,060	$ 1,550
Line of Credit Facility [Line Items]
Amount outstanding at period end	3,060	1,550
Letter of Credit
Line of Credit Facility [Abstract]
Amount outstanding at period end	92	92
Line of Credit Facility [Line Items]
Amount outstanding at period end	92	92
Letter of Credit \| Continuing Letter of Credit Agreement \| NSP-Minnesota
Line of Credit Facility [Abstract]
Credit Facility	50
Line of Credit Facility [Line Items]
Credit Facility	50
Letter of Credit \| Continuing Letter of Credit Agreement \| PSCo
Line of Credit Facility [Abstract]
Credit Facility	50
Line of Credit Facility [Line Items]
Credit Facility	50
Letter of Credit \| Continuing Letter of Credit Agreement \| SPS
Line of Credit Facility [Abstract]
Credit Facility	150
Line of Credit Facility [Line Items]
Credit Facility	150
Letter of Credit \| Continuing Letter of Credit Agreement \| XCEL ENERGY INC [Member]
Line of Credit Facility [Abstract]
Amount outstanding at period end	22
Line of Credit Facility [Line Items]
Amount outstanding at period end	22
Letter of Credit \| Bilateral Credit Agreement [Member] \| NSP-Minnesota
Line of Credit Facility [Abstract]
Amount outstanding at period end	59	59
Credit Facility	75	75
Line of Credit Facility [Line Items]
Amount outstanding at period end	59	59
Credit Facility	$ 75	$ 75