Accounting Pronouncements	12 Months Ended
Dec. 31, 2012
Accounting Pronouncements [Abstract]
Accounting Pronouncements	2. Accounting Pronouncements Recently Adopted Fair Value Measurement — In May 2011, the FASB issued Fair Value Measurement (Topic 820) — Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs (ASU No. 2011-04), which provides clarifications regarding existing fair value measurement principles and disclosure requirements, and also specific new guidance for items such as measurement of instruments classified within stockholders' equity. These requirements were effective for interim and annual periods beginning after Dec. 15, 2011. SPS implemented the accounting and disclosure guidance effective Jan. 1, 2012, and the implementation did not have a material impact on its financial statements. For required fair value measurement disclosures, see Notes 7 and 9. Presentation of Comprehensive Income — In June 2011, the FASB issued Comprehensive Income (Topic 220) — Presentation of Comprehensive Income (ASU No. 2011-05), which requires the presentation of the components of net income, the components of OCI and total comprehensive income in either a single continuous financial statement of comprehensive income or in two separate, but consecutive financial statements of net income and comprehensive income. These updates do not affect the items reported in OCI or the guidance for reclassifying such items to net income. These requirements were effective for interim and annual periods beginning after Dec. 15, 2011. SPS implemented the financial statement presentation guidance effective Jan. 1, 2012. Recently Issued Balance Sheet Offsetting — In December 2011, the FASB issued Balance Sheet (Topic 210) — Disclosures about Offsetting Assets and Liabilities (ASU No. 2011-11), which requires disclosures regarding netting arrangements in agreements underlying derivatives, certain financial instruments and related collateral amounts, and the extent to which an entity's financial statement presentation policies related to netting arrangements impact amounts recorded to the financial statements. In January 2013, the FASB issued Balance Sheet (Topic 210) – Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities (ASU 2013-01) to clarify the specific instruments and activities that should be considered in these disclosures. These disclosure requirements do not affect the presentation of amounts in the balance sheets, and are effective for annual reporting periods beginning on or after Jan. 1, 2013, and interim periods within those annual reporting periods. SPS does not expect the implementation of this disclosure guidance to have a material impact on its financial statements. Comprehensive Income Disclosures— In February 2013, the FASB issued Comprehensive Income (Topic 220) -– Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (ASU No. 2013-02), which requires detailed disclosures of the amounts reclassified out of accumulated other comprehensive income. These disclosure requirements do not change how net income or comprehensive income are presented in the financial statements. These disclosure requirements are effective for annual reporting periods beginning on or after Dec. 15, 2012, and interim periods within those annual reporting periods. SPS does not expect the implementation of this disclosure guidance to have a material impact on its financial statements.

2. Accounting Pronouncements

Recently Adopted

Fair Value Measurement — In May 2011, the FASB issued Fair Value Measurement (Topic 820) — Amendments to Achieve Common Fair Value Measurement and Disclosure Requirements in U.S. GAAP and IFRSs (ASU No. 2011-04), which provides clarifications regarding existing fair value measurement principles and disclosure requirements, and also specific new guidance for items such as measurement of instruments classified within stockholders' equity. These requirements were effective for interim and annual periods beginning after Dec. 15, 2011. SPS implemented the accounting and disclosure guidance effective Jan. 1, 2012, and the implementation did not have a material impact on its financial statements. For required fair value measurement disclosures, see Notes 7 and 9.

Presentation of Comprehensive Income — In June 2011, the FASB issued Comprehensive Income (Topic 220) — Presentation of Comprehensive Income (ASU No. 2011-05), which requires the presentation of the components of net income, the components of OCI and total comprehensive income in either a single continuous financial statement of comprehensive income or in two separate, but consecutive financial statements of net income and comprehensive income. These updates do not affect the items reported in OCI or the guidance for reclassifying such items to net income. These requirements were effective for interim and annual periods beginning after Dec. 15, 2011. SPS implemented the financial statement presentation guidance effective Jan. 1, 2012.

Recently Issued

Balance Sheet Offsetting — In December 2011, the FASB issued Balance Sheet (Topic 210) — Disclosures about Offsetting Assets and Liabilities (ASU No. 2011-11), which requires disclosures regarding netting arrangements in agreements underlying derivatives, certain financial instruments and related collateral amounts, and the extent to which an entity's financial statement presentation policies related to netting arrangements impact amounts recorded to the financial statements. In January 2013, the FASB issued Balance Sheet (Topic 210) – Clarifying the Scope of Disclosures about Offsetting Assets and Liabilities (ASU 2013-01) to clarify the specific instruments and activities that should be considered in these disclosures. These disclosure requirements do not affect the presentation of amounts in the balance sheets, and are effective for annual reporting periods beginning on or after Jan. 1, 2013, and interim periods within those annual reporting periods. SPS does not expect the implementation of this disclosure guidance to have a material impact on its financial statements.

Comprehensive Income Disclosures— In February 2013, the FASB issued Comprehensive Income (Topic 220) -– Reporting of Amounts Reclassified Out of Accumulated Other Comprehensive Income (ASU No. 2013-02), which requires detailed disclosures of the amounts reclassified out of accumulated other comprehensive income. These disclosure requirements do not change how net income or comprehensive income are presented in the financial statements. These disclosure requirements are effective for annual reporting periods beginning on or after Dec. 15, 2012, and interim periods within those annual reporting periods. SPS does not expect the implementation of this disclosure guidance to have a material impact on its financial statements.