Debt - Additional Information (Detail) - CRG Term Loan - USD ($)		1 Months Ended			9 Months Ended
	Jun. 26, 2015	Oct. 31, 2017	Apr. 30, 2017	May 31, 2016	Sep. 30, 2017	Mar. 31, 2016
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000,000
Current borrowing capacity	30,000,000		$ 5,000,000			$ 15,000,000
Remaining borrowing capacity	20,000,000					20,000,000
Post money valuation minimum amount	120,000,000
Debt drawn	$ 30,000,000			$ 15,000,000
Debt maturity date					Jun. 26, 2020
Debt interest-payment-only period					3 years
Frequency of periodic payment					Quarterly
Facility fee	7.00%
Term loan first amendment description					In March 2016, the Company and CRG executed an amendment to the original terms of the CRG Term Loan such that, with regard to the conditions for borrowing the remaining $20.0 million available under the CRG Term Loan, the Company may, at its election, draw down (i) an amount of either $10.0 million or $15.0 million in up to two advances upon achievement of a minimum of $15.0 million of aggregate product and service revenue during any consecutive 12 month period ending on or before March 31, 2016 and (ii) an additional $5.0 million (or $10.0 million, if the previous draw made was only in an amount of $10.0 million) upon achievement of a minimum of $25.0 million of aggregate product and service revenue during any consecutive 12 month period ending on or before December 31, 2016 and upon execution of the first sales contract of the Company?s second generation product.
Debt drawn					$ 0
Term loan second amendment description					In April 2017, the Company and CRG executed an amendment to the terms of its CRG Term Loan, as amended in March 2016. Amendments to the CRG Term Loan include availability of the existing $5.0 million tranche at ViewRay’s option through June 30, 2017, the addition of a $15.0 million tranche of borrowing capacity available at ViewRay’s option through September 30, 2017, extension of the interest-only and payment in-kind period, a decrease to the combined 2016 and 2017 revenue covenant and a 1.75% increase to the facility fee
Additional borrowing capacity			$ 15,000,000
Existing capacity extended expiration date			Jun. 30, 2017
Additional capacity extended expiration date			Sep. 30, 2017
Increase in facility fee			1.75%
Amount outstanding under the agreement					$ 45,000,000
Subsequent Event
Debt Instrument [Line Items]
Current borrowing capacity		$ 15,000,000
Existing capacity extended expiration date		Dec. 31, 2017
Term loan third amendment description		In October 2017, the Company and CRG executed another amendment to the terms of its CRG Term Loan, as amended in March 2016 and April 2017. This amendment extends the availability of the existing $15.0 million borrowing capacity through December 31, 2017.
Milestone One
Debt Instrument [Line Items]
Remaining borrowing capacity						10,000,000
Required minimum gross revenue						15,000,000
Milestone Two
Debt Instrument [Line Items]
Remaining borrowing capacity						5,000,000
Required minimum gross revenue						25,000,000
Debt drawn						15,000,000
Minimum
Debt Instrument [Line Items]
Proceeds from initial public offering	$ 40,000,000
Minimum | Milestone One
Debt Instrument [Line Items]
Debt drawn						10,000,000
Maximum | Milestone One
Debt Instrument [Line Items]
Remaining borrowing capacity						15,000,000
Debt drawn						15,000,000
Maximum | Milestone Two
Debt Instrument [Line Items]
Remaining borrowing capacity						$ 10,000,000
First 12 months
Debt Instrument [Line Items]
Debt instrument cash interest rate percentage	12.50%
Debt instrument cash interest rate percentage	8.00%
Deferred payment in-kind interest rate	4.50%
Prepayment penalty	3.00%
After Year 1 but on or Before Year 2
Debt Instrument [Line Items]
Debt instrument cash interest rate percentage	12.50%
Debt instrument cash interest rate percentage	8.00%
Deferred payment in-kind interest rate	4.50%
Prepayment penalty	2.00%
After Year 2 but on or Before Year 3
Debt Instrument [Line Items]
Debt instrument cash interest rate percentage	12.50%
Prepayment penalty	1.00%
After Year 3 Thereafter Until Maturity
Debt Instrument [Line Items]
Prepayment penalty	0.00%
MRIdian System
Debt Instrument [Line Items]
Required minimum gross revenue	$ 25,000,000