The Company and Its Significant Accounting Policies - Concentrations of Credit Risk (Details) - USD ($) $ in Millions	Jun. 30, 2026	Jun. 30, 2025
Accounting Policies [Abstract]
Allowance for potential credit losses related to accounts receivable and acquired card receivables	$ 28.3	$ 30.3

Accounts receivable, allowance for potential credit loss and acquired card receivables.

No definition available.

Name:	bill_AccountsReceivableAllowanceForPotentialCreditLossAndAcquiredCardReceivables
Namespace Prefix:	bill_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant