Joint Venture - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Dec. 31, 2019	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2018	Jan. 31, 2019
Schedule Of Equity Method Investments [Line Items]
Gain on contribution to joint venture		$ 12,964,000
Elimination of equity method investment intra-entity profit on sales		1,847,000
Accumulated deficit		(481,713,000)	$ (485,540,000)
Goodwill		57,717,000	57,770,000	$ 57,855,000
Impairment of goodwill		$ 0	$ 0	$ 0
Accuray Asia
Schedule Of Equity Method Investments [Line Items]
Percentage of ownership interest in joint venture		49.00%			49.00%
Gain on contribution to joint venture	$ 13,000,000.0
Elimination of equity method investment intra-entity profit on sales		$ 1,800,000
Proportion of recognizing joint venture income or loss		49.00%
Accumulated deficit		$ 100,000
Equity method investment		13,900,000
Proportional share of underlying equity in net assets		10,900,000
Equity method investment, intra-entity profit		1,800,000
Difference in equity method investment		3,000,000.0
Goodwill		4,800,000
Impairment of goodwill		$ 0