The earliest open tax year(s) subject to income tax examination by a taxing authority.

No definition available.

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- Definition

The potential income tax expense that could become payable in the event of a successful challenge by a taxing authority of an entity's income tax position.

+ References

No definition available.

+ Details

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- Definition

-- None. No documentation exists for this element. --

+ References

No definition available.

+ Details

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- Definition

Tax benefits associated with NOL and tax credit carryforwards that reduce unrecognized tax benefits.

+ References

No definition available.

+ Details

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- Definition

The tax year(s) being audited in connection with the income tax examination.

+ References

No definition available.

+ Details

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- Definition

The total amount of unrecognized tax benefits for which the ultimate deductibility is highly certain but for which there is uncertainty about the timing of such deductibility and, if recognized, would not affect the effective tax rate but would accelerate the payment of cash to the taxing authority to an earlier period.

+ References

No definition available.

+ Details

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- Definition

The tax year of a carryback claim under examination from a taxing authority.

+ References

No definition available.

+ Details

Name:	sps_Yearofcarrybackclaimunderexamination
Namespace Prefix:	sps_
Data Type:	xbrli:stringItemType
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- Definition

Amount of decrease reasonably possible in the next twelve months for the unrecognized tax benefit.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (d)(3)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

+ Details

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- References

No definition available.

+ Details

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- Definition

Amount of unrecognized tax benefits pertaining to uncertain tax positions taken in tax returns.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15A
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=SL6600010-109319

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Glossary Unrecognized Tax Benefit
-URI http://asc.fasb.org/extlink&oid=6527854

+ Details

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- Definition

Amount of statutory penalties accrued for a tax position claimed or expected to be claimed by the entity, in its tax return.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 740
-SubTopic 10
-Section 50
-Paragraph 15
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6907707&loc=d3e32718-109319

+ Details

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- Definition

The total amount of unrecognized tax benefits that, if recognized, would affect the effective tax rate.

+ References

+ Details

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- Details

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- Details

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- Details

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Income Taxes (Details) - USD ($)	3 Months Ended	9 Months Ended
Income Taxes (Details) - USD ($)	Mar. 31, 2016	Sep. 30, 2015	Sep. 30, 2012	Dec. 31, 2015
Unrecognized Tax Benefits [Abstract]
Unrecognized tax benefit - Permanent tax positions	$ 2,600,000			$ 2,600,000
Unrecognized tax benefit - Temporary tax positions	21,700,000			22,100,000
Total unrecognized tax benefit	24,300,000			24,700,000
NOL and tax credit carryforwards	(5,000,000)			(5,000,000)
Upper bound of decrease in unrecognized tax benefit that is reasonably possible	7,000,000
Amounts accrued for penalties related to unrecognized tax benefits	0			$ 0
Internal Revenue Service (IRS)
Tax Audits [Abstract]
Year(s) under examination		2012 and 2013	2010 and 2011
Year of carryback claim under examination			2009
Potential Tax Adjustments	$ 14,000,000
State Jurisdiction (Texas)
Tax Audits [Abstract]
Earliest year subject to examination	2009
TEXAS
Tax Audits [Abstract]
Year(s) under examination	2009 and 2010