Debt - Additional Information (Detail) - USD ($)		1 Months Ended				12 Months Ended
	Jun. 26, 2015	Oct. 31, 2017	Apr. 30, 2017	May 31, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2013	Dec. 31, 2016	Dec. 31, 2014
Debt Instrument [Line Items]
Warrant liability						$ 22,420,000		$ 2,723,000
Hercules Term Loan
Debt Instrument [Line Items]
Amount outstanding under the agreement									$ 15,000,000
Debt instrument, interest rate percentage							10.25%
Maturity Date Range, End							Jun. 01, 2017
Beginning period for monthly principal and interest payments							Jan. 01, 2015
Frequency of Periodic Payment						Monthly principal and interest payments
Beginning period for interest payments							Jan. 31, 2014
Unamortized debt discount							$ 466,000
Exercisable from Issuance							10 years
Exercisable after an IPO							5 years
Warrant liability							$ 158,000
Fair value of warrant assumption, expected term							2 years
Fair value of warrant assumption, expected volatility							30.00%
Fair value of warrant assumption, risk-free interest rate							0.40%
Fair value of warrant assumption, expected dividend yield							0.00%
Hercules Term Loan | Series C Convertible Preferred Stock
Debt Instrument [Line Items]
Vested and exercisable warrant to purchase							128,231
Exercise price							$ 5.84
Hercules Term Loan | First 12 months
Debt Instrument [Line Items]
Prepayment penalty							5.00%
Hercules Term Loan | Thereafter Until Maturity
Debt Instrument [Line Items]
Prepayment penalty							1.00%
Hercules Term Loan | Prime Rate
Debt Instrument [Line Items]
Spread on interest rate							7.00%
Hercules Term Loan | Deferred Payment In-Kind Interest
Debt Instrument [Line Items]
Debt instrument, interest rate percentage							1.50%
CRG Term Loan
Debt Instrument [Line Items]
Amount outstanding under the agreement						$ 45,000,000
Debt instrument, interest rate percentage	12.50%
Frequency of Periodic Payment						quarterly
Unamortized debt discount						$ 496,000
Maximum borrowing capacity	$ 50,000,000
Current borrowing capacity	30,000,000	$ 15,000,000	$ 5,000,000		$ 15,000,000
Remaining borrowing capacity	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		$ 0
Debt maturity date						Jun. 26, 2020
Interest payment end date						Mar. 31, 2020
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, 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		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 extends the availability of the $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, as amended in March 2016, April 2017 and October 2017, to decrease the amount of the minimum combined 2016 and 2017 revenue covenant.
Deferred payment in-kind interest						$ 4,800,000
CRG Term Loan | Milestone One
Debt Instrument [Line Items]
Remaining borrowing capacity					10,000,000
Required minimum gross revenue					15,000,000
CRG Term Loan | Milestone One | Minimum
Debt Instrument [Line Items]
Debt drawn					10,000,000
CRG Term Loan | Milestone One | Maximum
Debt Instrument [Line Items]
Remaining borrowing capacity					15,000,000
Debt drawn					15,000,000
CRG Term Loan | Milestone Two
Debt Instrument [Line Items]
Remaining borrowing capacity					5,000,000
Required minimum gross revenue					25,000,000
Debt drawn					15,000,000
CRG Term Loan | Milestone Two | Maximum
Debt Instrument [Line Items]
Remaining borrowing capacity					$ 10,000,000
CRG Term Loan | MRIdian System
Debt Instrument [Line Items]
Required minimum gross revenue	$ 25,000,000
CRG Term Loan | After Year 1 but on or Before Year 2
Debt Instrument [Line Items]
Prepayment penalty	2.00%
CRG Term Loan | After Year 2 but on or Before Year 3
Debt Instrument [Line Items]
Prepayment penalty	1.00%
CRG Term Loan | First 12 months
Debt Instrument [Line Items]
Prepayment penalty	3.00%
Debt instrument cash interest rate percentage	8.00%
Deferred payment in-kind interest rate	4.50%
CRG Term Loan | After Year 3 Thereafter Until Maturity
Debt Instrument [Line Items]
Prepayment penalty	0.00%