Merger - Additional Information (Details) $ / shares in Units, $ in Millions		12 Months Ended
	Jul. 23, 2015 USD ($) $ / shares shares	Dec. 31, 2017 $ / shares shares	Dec. 31, 2015	Dec. 31, 2016 $ / shares shares	Jul. 31, 2015 shares
Business Acquisition [Line Items]
Common stock, shares authorized	300,000,000	300,000,000		300,000,000
Preferred stock, shares authorized		10,000,000		10,000,000
Preferred stock, par value | $ / shares		$ 0.01		$ 0.01
Common stock, par value | $ / shares	$ 0.01	$ 0.01		$ 0.01
Reverse stock split, description			July 23, 2015, ViewRay Technologies, Inc. effected a 2.975-for-1 stock split of its then outstanding common stock and convertible preferred stock, collectively referred to as Capital Stock, and convertible preferred stock warrants, in which (i) each share of outstanding Capital Stock was increased into 2.975 shares of Capital Stock; (ii) the number of outstanding options to purchase each Capital Stock was proportionately increased on a 2.975-for-1 basis; (iii) number of shares reserved for future option grants under the 2008 Plan were proportionately increased on a 2.975-for-1 basis; (iv) the exercise price of each such outstanding option was proportionately decreased on a 2.975-for-1 basis; and (v) each share of outstanding convertible preferred stock warrant was increased into 2.975 shares of convertible preferred stock warrant. All of the share and per share amounts have been adjusted, on a retroactive basis, to reflect this 2.975-for-1 stock split.
Reverse stock split, conversion ratio	2.975
Common stock, shares outstanding		67,653,974		43,581,184
Common stock reserved for issuance		14,209,402		10,822,328
Options to purchase shares granted to employees		2,986,244
2008 Stock and 2015 Equity Incentive Plan
Business Acquisition [Line Items]
Percentage of common stock on diluted basis	19.30%
Common stock reserved for issuance	9,225,397
2015 Equity Incentive Plan
Business Acquisition [Line Items]
Options to purchase shares granted to employees	1,507,147
2015 Employee Stock Purchase Plan
Business Acquisition [Line Items]
Common stock reserved for issuance	285,621				667,670
Majority Shareholder
Business Acquisition [Line Items]
Percentage of stock owned by former stockholders	90.90%
Former Holders Of View Ray Technologies, Inc
Business Acquisition [Line Items]
Common stock, shares outstanding	34,715,582
Percentage of stock owned by former stockholders	72.70%
Convertible warrants	128,231
Percentage of common stock warrants on diluted basis	0.30%
Placement Agents
Business Acquisition [Line Items]
Percentage of common stock on diluted basis	0.40%
Common stock issued as warrants	198,760
Holders of Mirax
Business Acquisition [Line Items]
Common stock, shares outstanding	1,000,005
Percentage of common stock on diluted basis	2.10%
Private Placement
Business Acquisition [Line Items]
Private placement, value | $	$ 26.3
Private placement, common shares	5,884,504
Sales of share common stock, per share | $ / shares	$ 5.00
Percentage of common stock on diluted basis	12.30%
Private Placement | Investor
Business Acquisition [Line Items]
Private placement, value | $	$ 17.0
Private Placement | Share Holders of Mirax
Business Acquisition [Line Items]
Common stock, shares outstanding	1,000,005
Private Placement | Former Holders Of View Ray Technologies, Inc
Business Acquisition [Line Items]
Private placement, common shares	3,400,003
Private Placement | New Share Holders
Business Acquisition [Line Items]
Private placement, common shares	2,484,501
Blank Check Preferred Stock
Business Acquisition [Line Items]
Preferred stock, shares authorized	10,000,000
Preferred stock, par value | $ / shares	$ 0.01