Schedule Of Fair Values Of Assets And Liabilities Measured On Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	Jun. 30, 2012
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	$ 215,890
Total liabilities measured at fair value on a recurring basis	24,148
Derivative Financial Instruments, Liabilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total liabilities measured at fair value on a recurring basis	174
Contingent Liability For Acquisition
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total liabilities measured at fair value on a recurring basis	23,974
Money Market Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	32,709
Certificates of Deposit
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	120,361
Foreign Government Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	44,132
US Government Agencies Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	1,204
Auction Rate Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	17,175
Derivative Financial Instruments, Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	309
Fair Value, Inputs, Level 1
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	198,406
Fair Value, Inputs, Level 1 \| Money Market Funds
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	32,709
Fair Value, Inputs, Level 1 \| Certificates of Deposit
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	120,361
Fair Value, Inputs, Level 1 \| Foreign Government Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	44,132
Fair Value, Inputs, Level 1 \| US Government Agencies Debt Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	1,204
Fair Value, Inputs, Level 2
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	309
Total liabilities measured at fair value on a recurring basis	174
Fair Value, Inputs, Level 2 \| Derivative Financial Instruments, Liabilities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total liabilities measured at fair value on a recurring basis	174
Fair Value, Inputs, Level 2 \| Derivative Financial Instruments, Assets
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	309
Fair Value, Inputs, Level 3
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	17,175
Total liabilities measured at fair value on a recurring basis	23,974
Fair Value, Inputs, Level 3 \| Contingent Liability For Acquisition
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total liabilities measured at fair value on a recurring basis	23,974
Fair Value, Inputs, Level 3 \| Auction Rate Securities
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Total assets measured at fair value on a recurring basis	$ 17,175

ARIBA INC 10-Q