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The Company and Its Significant Accounting Policies - Additional Information (Details) $ / shares in Units, $ in Thousands			3 Months Ended		6 Months Ended
	Dec. 16, 2019 USD ($) $ / shares shares	Nov. 27, 2019	Dec. 31, 2019 USD ($) Customer shares	Dec. 31, 2018 Customer	Dec. 31, 2019 USD ($) Segment Customer shares	Dec. 31, 2018 Customer	Aug. 02, 2018
Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Line Items]
Net proceeds from IPO \| $	$ 225,500				$ 226,565
Reclassification of redeemable convertible preferred stock warrant liabilities to additional paid-in capital upon initial public offering \| $	$ 1,400		$ 1,405		$ 1,405
Reverse split of shares description					On November 27, 2019, the Company filed an amendment to its amended and restated certificate of incorporation to effect a reverse split of shares of the Company’s issued and outstanding redeemable convertible preferred stock, common stock and non-voting common stock on a 2-for-1 basis.
Stock split, conversion ratio		2
Number of operating segments \| Segment					1
Total Revenue \| Customer Concentration Risk
Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Line Items]
Number of customers exceed 10% of revenue \| Customer			0	0	0	0
Concentration percentage			10.00%	10.00%	10.00%	10.00%
Common Stock
Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Line Items]
Shares issued \| shares			11,297,000		11,297,000
Redeemable convertible preferred stock converted (in shares) \| shares	52,434,505
IPO
Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Line Items]
Shares issued \| shares	11,297,058
Shares issued price to public per share \| $ / shares	$ 22.00
Underwriting discounts and commissions \| $	$ 17,400
Other offering costs \| $	$ 5,600
Over-Allotment Option
Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Line Items]
Shares issued \| shares	1,473,529
Bill.com, Inc \| BDC
Organization Consolidation Basis Of Presentation Business Description And Accounting Policies [Line Items]
Noncontrolling Interest, Ownership Percentage by Parent							100.00%