Borrowings and Other Financing Instruments, Capital Stock (Details) - $ / shares	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Capital Stock [Abstract]
Common Stock, Shares Authorized (in shares)	1,000,000,000		1,000,000,000
Common Stock, Par Value (in dollars per share)	$ 2.50		$ 2.50
Common Stock, Shares Outstanding (in shares)	507,535,523	506,959,395	505,733,267
Xcel Energy Inc.
Capital Stock [Abstract]
Preferred Stock, Shares Authorized (in shares)	7,000,000
Preferred Stock, Par Value (in dollars per share)	$ 100
Preferred Stock, Shares Outstanding (in shares)	0		0
Common Stock, Shares Outstanding (in shares)	507,535,523		505,733,267
PSCo
Capital Stock [Abstract]
Preferred Stock, Shares Authorized (in shares)	10,000,000
Preferred Stock, Par Value (in dollars per share)	$ 0.01
Preferred Stock, Shares Outstanding (in shares)	0		0
SPS
Capital Stock [Abstract]
Preferred Stock, Shares Authorized (in shares)	10,000,000
Preferred Stock, Par Value (in dollars per share)	$ 1.00
Preferred Stock, Shares Outstanding (in shares)	0		0