Debt - Additional Information (Detail) - USD ($)			1 Months Ended			3 Months Ended
	Mar. 31, 2016	Jun. 26, 2015	Oct. 31, 2017	Apr. 30, 2017	May 31, 2016	Mar. 31, 2018
Debt Instrument [Line Items]
Maximum borrowing capacity		$ 50,000,000
Current borrowing capacity	$ 15,000,000	30,000,000	$ 15,000,000	$ 5,000,000
Remaining borrowing capacity	20,000,000	20,000,000
Proceeds from initial public offering		40,000,000
Post Money Valuation Minimum Amount		120,000,000
Debt drawn		$ 30,000,000	$ 0		$ 15,000,000
Debt maturity date						Jun. 26, 2020
Interest payment end date						Mar. 31, 2020
Frequency of periodic payment						quarterly
Debt instrument cash interest rate percentage		12.50%
Debt instrument cash interest rate percentage		8.00%
Deferred payment in-kind interest rate		4.50%
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.
Term loan second amendment description						In April 2017, the Company and CRG executed an amendment to the terms of its CRG Term Loan. 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			Dec. 31, 2017	Jun. 30, 2017
Additional capacity extended expiration date				Sep. 30, 2017
Increase in facility fee				1.75%
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 extended the availability of the existing $15.0 million borrowing capacity through December 31, 2017.
Term loan fourth amendment description						In February 2018, the Company and CRG executed an amendment to the terms of its CRG Term Loan to decrease the amount of the minimum combined 2016 and 2017 revenue covenant.
Amount outstanding under the agreement						$ 45,000,000
Deferred payment in-kind interest						$ 5,300,000
Milestone One
Debt Instrument [Line Items]
Remaining borrowing capacity	10,000,000
Required minimum gross revenue	15,000,000
Milestone One | Maximum
Debt Instrument [Line Items]
Remaining borrowing capacity	15,000,000
Debt drawn	15,000,000
Milestone One | Minimum
Debt Instrument [Line Items]
Debt drawn	10,000,000
Milestone Two
Debt Instrument [Line Items]
Remaining borrowing capacity	5,000,000
Required minimum gross revenue	25,000,000
Debt drawn	15,000,000
Milestone Two | Maximum
Debt Instrument [Line Items]
Remaining borrowing capacity	$ 10,000,000
First 12 Months
Debt Instrument [Line Items]
Prepayment penalty		3.00%
After Year 1 but on or Before Year 2
Debt Instrument [Line Items]
Prepayment penalty		2.00%
After Year 2 but on or Before Year 3
Debt Instrument [Line Items]
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