Borrowings and Other Financing Instruments Borrowings and Other Financing Instruments, Long-Term Borrowings (Details) - Bonds [Member] $ in Millions	Jun. 30, 2019 USD ($)
PSCo | Series Due September 15, 2049 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 400
Debt Instrument, Interest Rate, Stated Percentage	4.05%
XCEL ENERGY INC [Member] | Series Due June 15, 2028 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 130
Debt Instrument, Interest Rate, Stated Percentage	4.00%
SPS | Series Due June 15, 2049 [Domain]
Debt Instrument [Line Items]
Debt Instrument, Face Amount	$ 300
Debt Instrument, Interest Rate, Stated Percentage	3.75%