Schedule I, Condensed Financial Statements of Xcel Energy Inc, Condensed Statements of Income (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income
Income (Loss) from Equity Method Investments									$ 35	$ 30	$ 42
Expenses and other deductions
Other income									14	10	18
Interest charges and financing costs									700	663	647
Income before income taxes									1,442	1,690	1,704
Income tax benefit									181	542	581
Net income	$ 214	$ 491	$ 265	$ 291	$ 189	$ 492	$ 227	$ 239	1,261	1,148	1,123
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Pension and retiree medical benefits, net of tax of $1, $3 and $(3) respectively									(6)	(3)	(8)
Other Comprehensive Income (Loss), Net of Tax									1	7
Comprehensive Income, Net of Tax									$ 1,262	$ 1,155	$ 1,123
Weighted average common shares outstanding:
Basic (in shares)									511	509	509
Diluted (in shares)									511	509	509
Earnings per average common share:
Basic (in dollars per share)	$ 0.42	$ 0.96	$ 0.52	$ 0.57	$ 0.37	$ 0.97	$ 0.45	$ 0.47	$ 2.47	$ 2.26	$ 2.21
Diluted (in dollars per share)	0.42	0.96	0.52	0.57	0.37	0.97	0.45	0.47	2.47	2.25	2.21
Cash dividends declared per common share (in dollars per share)	$ 0.38	$ 0.38	$ 0.38	$ 0.38	$ 0.36	$ 0.36	$ 0.36	$ 0.36	$ 1.52	$ 1.44	$ 1.36
Xcel Energy Inc.
Income
Income (Loss) from Equity Method Investments									$ 1,393	$ 1,263	$ 1,199
Total income									1,393	1,263	1,199
Expenses and other deductions
Operating expenses									24	30	22
Other income									(1)	(6)	(3)
Interest charges and financing costs									149	128	116
Total expenses and other deductions									172	152	135
Income before income taxes									1,221	1,111	1,064
Income tax benefit									(40)	(37)	(59)
Net income									1,261	1,148	1,123
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Pension and retiree medical benefits, net of tax of $1, $3 and $(3) respectively									3	4	(4)
Derivative instruments, net of tax of $(1), $2 and $2, respectively									(2)	3	4
Other Comprehensive Income (Loss), Net of Tax									1	7	0
Comprehensive Income, Net of Tax									$ 1,262	$ 1,155	$ 1,123