Basis of Presentation	3 Months Ended
Mar. 31, 2018
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements for the three-month periods ended March 31, 2018 and 2017 are unaudited. In the opinion of management, all adjustments necessary for a fair presentation of the consolidated financial statements have been included. Such adjustments consisted of normal recurring items. Interim results are not necessarily indicative of results for a full year. The consolidated financial statements and accompanying notes are presented as permitted by Form 10-Q and do not contain certain information included in the annual consolidated financial statements and accompanying notes of Fiserv, Inc. (the “Company”). These interim consolidated financial statements should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017. Effective January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers, and its related amendments (collectively known as “ASC 606”) using the modified retrospective transition approach applied to all contracts. Certain prior period amounts have been reclassified to conform to current period presentation. Additional information about the Company’s revenue recognition policies and the related impact of the adoption is included in Notes 2 and 3 to the consolidated financial statements. Principles of Consolidation The consolidated financial statements include the accounts of Fiserv, Inc. and all 100% owned subsidiaries. Investments in less than 50% owned affiliates in which the Company has significant influence but not control are accounted for using the equity method of accounting. All intercompany transactions and balances have been eliminated in consolidation. Stock Split On February 21, 2018, the Company’s board of directors declared a two-for-one stock split of the Company’s common stock and a proportionate increase in the number of its authorized shares of common stock. The additional shares were distributed on March 19, 2018 to shareholders of record at the close of business on March 5, 2018. The Company’s common stock began trading at the split-adjusted price on March 20, 2018. All share and per share amounts are retroactively presented on a split-adjusted basis. The impact on the consolidated balance sheets of the stock split was an increase of $4 million to common stock and an offsetting reduction in additional paid-in capital, which has been retroactively restated.

Basis of Presentation

The consolidated financial statements for the three-month periods ended March 31, 2018 and 2017 are unaudited. In the opinion of management, all adjustments necessary for a fair presentation of the consolidated financial statements have been included. Such adjustments consisted of normal recurring items. Interim results are not necessarily indicative of results for a full year. The consolidated financial statements and accompanying notes are presented as permitted by Form 10-Q and do not contain certain information included in the annual consolidated financial statements and accompanying notes of Fiserv, Inc. (the “Company”). These interim consolidated financial statements should be read in conjunction with the consolidated financial statements and accompanying notes included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2017.

Effective January 1, 2018, the Company adopted ASU 2014-09, Revenue from Contracts with Customers, and its related amendments (collectively known as “ASC 606”) using the modified retrospective transition approach applied to all contracts. Certain prior period amounts have been reclassified to conform to current period presentation. Additional information about the Company’s revenue recognition policies and the related impact of the adoption is included in Notes 2 and 3 to the consolidated financial statements.

Principles of Consolidation

The consolidated financial statements include the accounts of Fiserv, Inc. and all 100% owned subsidiaries. Investments in less than 50% owned affiliates in which the Company has significant influence but not control are accounted for using the equity method of accounting. All intercompany transactions and balances have been eliminated in consolidation.

Stock Split

On February 21, 2018, the Company’s board of directors declared a two-for-one stock split of the Company’s common stock and a proportionate increase in the number of its authorized shares of common stock. The additional shares were distributed on March 19, 2018 to shareholders of record at the close of business on March 5, 2018. The Company’s common stock began trading at the split-adjusted price on March 20, 2018. All share and per share amounts are retroactively presented on a split-adjusted basis. The impact on the consolidated balance sheets of the stock split was an increase of $4 million to common stock and an offsetting reduction in additional paid-in capital, which has been retroactively restated.