Accounting Pronouncements	12 Months Ended
Dec. 31, 2011
Accounting Pronouncements [Abstract]
Accounting Pronouncements	2. Accounting Pronouncements Recently Issued 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 IFRS (ASU No. 2011-04), which provides additional guidance for fair value measurements. These updates to the Codification include 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 updates to the Codification are effective for interim and annual periods beginning after Dec. 15, 2011. SPS does not expect the implementation of this guidance to have a material impact on its financial statements. Comprehensive Income - In June 2011, the FASB issued Comprehensive Income (Topic 220) - Presentation of Comprehensive Income (ASU No. 2011-05), which updates the Codification to require the presentation of the components of net income, the components of OCI and total comprehensive income in either a single continuous statement of comprehensive income or in two separate, but consecutive 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 updates to the Codification are effective for interim and annual periods beginning after Dec. 15, 2011. SPS does not expect the implementation of this presentation guidance to have a material impact on its financial statements. Balance Sheet Offsetting - In December 2011, the FASB issued Balance Sheet (Topic 210) - Disclosures about Offsetting Assets and Liabilities (ASU No. 2011-11), which updates the Codification to require 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. These updates to the disclosure requirements of the Codification 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 periods. SPS does not expect the implementation of this disclosure guidance to have a material impact on its financial statements.

2. Accounting Pronouncements

Recently Issued

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 IFRS (ASU No. 2011-04), which provides additional guidance for fair value measurements. These updates to the Codification include 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 updates to the Codification are effective for interim and annual periods beginning after Dec. 15, 2011. SPS does not expect the implementation of this guidance to have a material impact on its financial statements.

Comprehensive Income - In June 2011, the FASB issued Comprehensive Income (Topic 220) - Presentation of Comprehensive Income (ASU No. 2011-05), which updates the Codification to require the presentation of the components of net income, the components of OCI and total comprehensive income in either a single continuous statement of comprehensive income or in two separate, but consecutive 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 updates to the Codification are effective for interim and annual periods beginning after Dec. 15, 2011. SPS does not expect the implementation of this presentation guidance to have a material impact on its financial statements.

Balance Sheet Offsetting - In December 2011, the FASB issued Balance Sheet (Topic 210) - Disclosures about Offsetting Assets and Liabilities (ASU No. 2011-11), which updates the Codification to require 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. These updates to the disclosure requirements of the Codification 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 periods. SPS does not expect the implementation of this disclosure guidance to have a material impact on its financial statements.