Related Party Transactions (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Operating revenues [Abstract]
Electric	$ 1,331	$ 6,539	$ 7,187
Operating expenses [Abstract]
Purchased power	8,136	9,271	10,896
Other operating expenses - paid to Xcel Energy Services Inc.	127,669	117,277	118,370
Interest expense	178	76	83
Interest income	0	10	1
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	15,840	4,791
Accounts payable	15,387	12,363
NSP-Minnesota
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	3,462	3,820
Accounts payable	0	0
NSP-Wisconsin
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	0	4
Accounts payable	26	0
PSCo
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	0	0
Accounts payable	1,056	69
Other Subsidiaries of Xcel Energy Inc.
Accounts Receivable and Payable with Affiliates [Abstract]
Accounts receivable	12,378	967
Accounts payable	$ 14,305	$ 12,294