Segment Information (Narrative) (Details)	12 Months Ended
Sep. 30, 2011
Segment Information
Segment reporting, factors used to identify entity's reportable segments	The Company's chief operating decision-maker currently reviews financial information presented on a consolidated basis, accompanied by disaggregated information about revenues for purposes of allocating resources and evaluating financial performance. Accordingly, management considers the Company to have a single operating segment, compared to the prior year periods presented below where three operating segments were reportable. The prior year information below is presented on a basis consistent with the determination of one operating segment in the current year. Management evaluates performance based on several factors including revenues and operating income. The results are based on the Company's method of internal reporting, which may not allocate income and expenses (such as amortization of intangible assets, stock-based compensation and other items included in the table below) that management does not believe are indicative of the ongoing operating performance of the Company, and are not necessarily in conformity with GAAP.
Description of products and services	Network revenues consist of network-related software access and transaction fees. Subscription software application revenues consist mainly of software access subscription fees. Maintenance revenues consist primarily of Ariba Buyer and Ariba Sourcing product maintenance fees. Services and other revenues consist of fees for implementation services, consulting services, training, education, premium support, and other miscellaneous items.

Segment Information (Narrative) (Details)

12 Months Ended

Sep. 30, 2011

Segment reporting, factors used to identify entity's reportable segments

The Company's chief operating decision-maker currently reviews financial information presented on a consolidated basis, accompanied by disaggregated information about revenues for purposes of allocating resources and evaluating financial performance. Accordingly, management considers the Company to have a single operating segment, compared to the prior year periods presented below where three operating segments were reportable. The prior year information below is presented on a basis consistent with the determination of one operating segment in the current year. Management evaluates performance based on several factors including revenues and operating income. The results are based on the Company's method of internal reporting, which may not allocate income and expenses (such as amortization of intangible assets, stock-based compensation and other items included in the table below) that management does not believe are indicative of the ongoing operating performance of the Company, and are not necessarily in conformity with GAAP.

Description of products and services

Network revenues consist of network-related software access and transaction fees. Subscription software application revenues consist mainly of software access subscription fees. Maintenance revenues consist primarily of Ariba Buyer and Ariba Sourcing product maintenance fees. Services and other revenues consist of fees for implementation services, consulting services, training, education, premium support, and other miscellaneous items.