Background and Basis of Presentation	6 Months Ended
Background and Basis of Presentation	Jun. 30, 2011
Background and Basis of Presentation [Abstract]
BACKGROUND AND BASIS OF PRESENTATION	1. BACKGROUND AND BASIS OF PRESENTATION S1 Corporation is a leading global provider of payments and financial services software solutions. We offer payments solutions for ATM and retail point-of-sale (“POS”) driving, card management, and merchant acquiring, as well as financial services solutions for consumer, small business and corporate online banking, trade finance, mobile banking, voice banking, branch and call center banking. We sell our solutions primarily to banks, credit unions, retailers and transaction processors. We also provide software, custom software development, hosting and other services to State Farm Mutual Automobile Insurance Company (“State Farm”), a relationship that we expect will conclude by the end of 2011. When we use the terms “S1 Corporation”, “S1”, “Company”, “we”, “us” and “our,” we mean S1 Corporation, a Delaware corporation, and its subsidiaries. We have prepared the accompanying unaudited condensed consolidated financial statements and condensed notes pursuant to the rules and regulations of the Securities and Exchange Commission (“SEC”) regarding interim financial reporting. Accordingly, they do not contain all of the information and notes required by accounting principles generally accepted in the United States of America (“U.S. GAAP”) for complete financial statements and should be read in conjunction with the consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the fiscal year ended December 31, 2010. In our opinion, the accompanying unaudited condensed consolidated financial statements reflect all adjustments (consisting of only normal recurring adjustments) considered necessary for a fair statement of our financial position as of June 30, 2011, our results of operations for the three months and six months ended June 30, 2011, and our cash flows for the six months ended June 30, 2011. The data in the condensed consolidated balance sheet as of December 31, 2010 was derived from our audited consolidated balance sheet as of December 31, 2010, as presented in our Annual Report on Form 10-K for the fiscal year ended December 31, 2010. The unaudited condensed consolidated financial statements include the accounts of S1 and its wholly owned subsidiaries after the elimination of all significant intercompany accounts and transactions. Our operating results for the three months and six months ended June 30, 2011 are not necessarily indicative of the operating results that may be expected for the full year ending December 31, 2011 or for any other period. Certain amounts in the prior years’ consolidated financial statements have been reclassified to conform to the current year presentation.

Description containing the entire organization, consolidation and basis of presentation of financial statements disclosure. May be provided in more than one note to the financial statements, as long as users are provided with an understanding of (1) the significant judgments and assumptions made by an enterprise in determining whether it must consolidate a VIE and/or disclose information about its involvement with a VIE, (2) the nature of restrictions on a consolidated VIE's assets reported by an enterprise in its statement of financial position, including the carrying amounts of such assets, (3) the nature of, and changes in, the risks associated with an enterprise's involvement with the VIE, and (4) how an enterprise's involvement with the VIE affects the enterprise's financial position, financial performance, and cash flows. Describes procedure if disclosures are provided in more than one note to the financial statements.

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