Fair Value of Financial Assets and Liabilities, Derivative Assets and Liabilities at Fair Value (Details) (Fair Value Measured on a Recurring Basis, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013		Dec. 31, 2012
Other Current Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	$ 100,215		$ 69,013
Other Current Assets [Member] | Purchased Power Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	33,026	[1]	32,717	[1]
Other Current Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	67,189		36,296
Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	61		95
Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	17,849		20,320
Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	47,282		15,881
Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,997		0
Other Noncurrent Assets [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	100,313		126,297
Other Noncurrent Assets [Member] | Purchased Power Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	74,789	[1]	89,061	[1]
Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	25,524		37,236
Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	12		39
Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	25,512		37,197
Other Current Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	29,897		32,482
Other Current Liabilities [Member] | Purchased Power Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	23,144	[1]	22,880	[1]
Other Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	6,753		9,602
Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	6,524		9,511
Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	229		91
Other Noncurrent Liabilities [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	222,575		242,866
Other Noncurrent Liabilities [Member] | Purchased Power Agreements [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	215,258	[1]	225,659	[1]
Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	7,317		17,207
Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	7,317		17,207
Level 1 | Other Current Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 1 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 1 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 1 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 1 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 1 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 1 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 1 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 1 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 1 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 1 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 1 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 1 | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 1 | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 2 | Other Current Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	25,568		26,405
Level 2 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	61		95
Level 2 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	23,508		26,303
Level 2 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 2 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,999		7
Level 2 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	28,893		41,368
Level 2 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	26		86
Level 2 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	28,867		41,282
Level 2 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	15,347		18,720
Level 2 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	15,116		18,622
Level 2 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 2 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	231		98
Level 2 | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	10,741		21,417
Level 2 | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	10,741		21,417
Level 3 | Other Current Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	52,454		17,416
Level 3 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 3 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	2,349		692
Level 3 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	50,105		16,724
Level 3 | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 3 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	55		77
Level 3 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0		0
Level 3 | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	55		77
Level 3 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	5,291		844
Level 3 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	2,468		1
Level 3 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	2,823		843
Level 3 | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 3 | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Level 3 | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	0		0
Fair Value Total [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	78,022		43,821
Fair Value Total [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	61		95
Fair Value Total [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	25,857		26,995
Fair Value Total [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	50,105		16,724
Fair Value Total [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	1,999		7
Fair Value Total [Member] | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	28,948		41,445
Fair Value Total [Member] | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	26		86
Fair Value Total [Member] | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	28,922		41,359
Fair Value Total [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	20,638		19,564
Fair Value Total [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	17,584		18,623
Fair Value Total [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	2,823		843
Fair Value Total [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	231		98
Fair Value Total [Member] | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	10,741		21,417
Fair Value Total [Member] | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	10,741		21,417
Counterparty Netting [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	(10,833)	[2]	(7,525)	[3]
Counterparty Netting [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	0	[2]	0	[3]
Counterparty Netting [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	(8,008)	[2]	(6,675)	[3]
Counterparty Netting [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	(2,823)	[2]	(843)	[3]
Counterparty Netting [Member] | Other Current Assets [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	(2)	[2]	(7)	[3]
Counterparty Netting [Member] | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	(3,424)	[2]	(4,209)	[3]
Counterparty Netting [Member] | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Vehicle Fuel And Other Commodity [Member] | Cash Flow Hedges [Member]
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	(14)	[2]	(47)	[3]
Counterparty Netting [Member] | Other Noncurrent Assets [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Asset, Fair Value, Gross Asset	(3,410)	[2]	(4,162)	[3]
Counterparty Netting [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(13,885)	[2]	(9,962)	[3]
Counterparty Netting [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(11,060)	[2]	(9,112)	[3]
Counterparty Netting [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Electric Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(2,823)	[2]	(843)	[3]
Counterparty Netting [Member] | Other Current Liabilities [Member] | Designated as Hedging Instrument [Member] | Natural Gas Commodity [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(2)	[2]	(7)	[3]
Counterparty Netting [Member] | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	(3,424)	[2]	(4,210)	[3]
Counterparty Netting [Member] | Other Noncurrent Liabilities [Member] | Designated as Hedging Instrument [Member] | Commodity Trading
Derivatives, Fair Value [Line Items]
Derivative Liability, Fair Value, Gross Liability	$ (3,424)	[2]	$ (4,210)	[3]

[1] In 2003, as a result of implementing new guidance on the normal purchase exception for derivative accounting, Xcel Energy began recording several long-term purchased power agreements at fair value due to accounting requirements related to underlying price adjustments. As these purchases are recovered through normal regulatory recovery mechanisms in the respective jurisdictions, the changes in fair value for these contracts were offset by regulatory assets and liabilities. During 2006, Xcel Energy qualified these contracts under the normal purchase exception. Based on this qualification, the contracts are no longer adjusted to fair value and the previous carrying value of these contracts will be amortized over the remaining contract lives along with the offsetting regulatory assets and liabilities.

[2] Xcel Energy nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at June 30, 2013. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.

[3] Xcel Energy nets derivative instruments and related collateral in its consolidated balance sheet when supported by a legally enforceable master netting agreement, and all derivative instruments and related collateral amounts were subject to master netting agreements at Dec. 31, 2012. The counterparty netting amounts presented exclude settlement receivables and payables and non-derivative amounts that may be subject to the same master netting agreements.