ViewRay (VRAYQ) 10-K 12 Mar 18 2017 FY Annual report Financial data

Document and Entity Information

Document and Entity Information - USD ($)	12 Months Ended
	Dec. 31, 2017	Mar. 02, 2018	Jun. 30, 2017
Document And Entity Information [Abstract]
Entity Registrant Name	ViewRay, Inc.
Entity Central Index Key	1,597,313
Document Type	10-K
Trading Symbol	VRAY
Document Period End Date	Dec. 31, 2017
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		67,653,974
Entity Public Float			$ 166,918,728
Entity Current Reporting Status	Yes
Entity Voluntary Filers	No
Entity Well-known Seasoned Issuer	No
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2,017

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents	$ 57,389	$ 14,198
Accounts receivable	20,326	4,200
Inventory	19,375	8,082
Deposits on purchased inventory	7,043	2,522
Deferred cost of revenue	13,696	3,909
Prepaid expenses and other current assets	4,862	3,023
Total current assets	122,691	35,934
Property and equipment, net	11,564	11,560
Restricted cash	1,143	1,143
Intangible assets, net	78	97
Other assets	235	30
TOTAL ASSETS	135,711	48,764
Current liabilities:
Accounts payable	11,014	4,980
Accrued liabilities	7,207	6,334
Customer deposits	17,820	19,400
Deferred revenue, current portion	20,151	6,515
Total current liabilities	56,192	37,229
Deferred revenue, net of current portion	3,238	3,918
Long-term debt	44,504	44,290
Warrant liability	22,420	2,723
Other long-term liabilities	7,370	4,257
TOTAL LIABILITIES	133,724	92,417
Commitments and contingencies (Note 7)
Stockholders’ equity (deficit):
Convertible preferred stock, par value $0.01 per share; 10,000,000 shares authorized at December 31, 2017 and 2016; no shares issued and outstanding at December 31, 2017 and 2016	0	0
Common stock, par value of $0.01 per share; 300,000,000 shares authorized at December 31, 2017 and 2016; 67,653,974 and 43,581,184 shares issued and outstanding at December 31, 2017 and 2016	666	426
Additional paid-in capital	321,174	203,598
Accumulated deficit	(319,853)	(247,677)
TOTAL STOCKHOLDERS’ EQUITY (DEFICIT)	1,987	(43,653)
TOTAL LIABILITIES AND STOCKHOLDERS’ EQUITY (DEFICIT)	$ 135,711	$ 48,764

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - $ / shares	Dec. 31, 2017	Dec. 31, 2016
Statement Of Financial Position [Abstract]
Preferred stock, par value (in dollar per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized	10,000,000	10,000,000
Preferred stock, shares issued	0	0
Preferred stock, shares outstanding	0	0
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	300,000,000	300,000,000
Common stock, shares issued	67,653,974	43,581,184
Common stock, shares outstanding	67,653,974	43,581,184

Consolidated Statements of Oper

Consolidated Statements of Operations and Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue:
Product	$ 30,458	$ 20,555	$ 9,620
Service	3,109	1,504	530
Distribution rights	475	178	0
Grant	0	0	240
Total revenue	34,042	22,237	10,390
Cost of revenue:
Product	25,488	23,897	12,673
Service	2,222	1,969	1,871
Total cost of revenue	27,710	25,866	14,544
Gross margin	6,332	(3,629)	(4,154)
Operating expenses:
Research and development	14,709	11,442	10,449
Selling and marketing	8,412	5,601	5,139
General and administrative	31,375	23,503	21,685
Total operating expenses	54,496	40,546	37,273
Loss from operations	(48,164)	(44,175)	(41,427)
Interest income	5	2	2
Interest expense	(7,247)	(5,951)	(3,452)
Other expense, net	(16,770)	(512)	(117)
Loss before provision for income taxes	(72,176)	(50,636)	(44,994)
Provision for income taxes	0	0	1
Net loss and comprehensive loss	$ (72,176)	$ (50,636)	$ (44,995)
Net loss per share, basic and diluted	$ (1.23)	$ (1.26)	$ (2.58)
Weighted-average common shares used to compute net loss per share attributable to common stockholders, basic and diluted	58,457,868	40,068,307	17,432,434

Consolidated Statements of Conv

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) - USD ($) $ in Thousands	Total	Private Placement	Direct Registered Offering	At The Market Offering Program	Convertible Preferred Stock	Common Stock	Common StockPrivate Placement	Common StockDirect Registered Offering	Common StockAt The Market Offering Program	Common StockHolders of Mirax	Additional Paid-in Capital	Additional Paid-in CapitalPrivate Placement	Additional Paid-in CapitalDirect Registered Offering	Additional Paid-in CapitalAt The Market Offering Program	Accumulated Deficit
Balance at Dec. 31, 2014	$ (150,623)					$ 9					$ 1,414				$ (152,046)
Temporary equity balance , shares at Dec. 31, 2014					27,654,928
Temporary equity balance at Dec. 31, 2014					$ 145,110
Balance, shares at Dec. 31, 2014						907,037
Issuance of common stock from option exercises	24										24
Issuance of common stock from option exercises, shares						31,427
Stock-based compensation	1,066										1,066
Issuance of Series C convertible preferred stock (net of issuance costs of $221)					$ 15,729
Issuance of Series C convertible preferred stock (net of issuance costs of $221), shares					2,727,059
Conversion of convertible securities, value	160,839				$ (160,839)	$ 304					160,535
Conversion of convertible securities, shares					(30,381,987)	30,381,987
Issuance of common stock, value		$ 26,323					$ 59					$ 26,264
Issuance of common stock, shares							5,884,504			1,000,005
Conversion of convertible preferred stock warrants into common stock warrants in connection with the Merger	93										93
Issuance of common stock warrants to placement agent as payment for services	316										316
Net loss	(44,995)														(44,995)
Balance at Dec. 31, 2015	(6,957)					$ 372					189,712				(197,041)
Balance, shares at Dec. 31, 2015						38,204,960
Issuance of common stock from option exercises	539					$ 8					531
Issuance of common stock from option exercises, shares						773,718
Stock-based compensation	2,907										2,907
Issuance of common stock, value		10,494					$ 46					10,448
Issuance of common stock, shares							4,602,506
Net loss	(50,636)														(50,636)
Balance at Dec. 31, 2016	(43,653)					$ 426					203,598				(247,677)
Balance, shares at Dec. 31, 2016						43,581,184
Issuance of common stock from option exercises	$ 665					$ 4					661
Issuance of common stock from option exercises, shares	420,377					420,377
Issuance of common stock from releases of restricted stock units, shares						57,626
Stock-based compensation	$ 5,319										5,319
Issuance of common stock, value		$ 22,616	$ 49,860	$ 38,979			$ 86	$ 84	$ 66			$ 22,530	$ 49,776	$ 38,913
Issuance of common stock, shares				0			8,602,589	8,382,643	6,575,062
Issuance of common stock from warrant exercises	103										103
Issuance of common stock from warrant exercises, shares						34,493
Reclassification of warrant liability to additional paid-in capital upon warrant exercises	274										274
Net loss	(72,176)														(72,176)
Balance at Dec. 31, 2017	$ 1,987					$ 666					$ 321,174				$ (319,853)
Balance, shares at Dec. 31, 2017						67,653,974

Consolidated Statements of Con6

Consolidated Statements of Convertible Preferred Stock and Stockholders' Equity (Deficit) (Parenthetical) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Private Placement
Offering cost	$ 111	$ 529	$ 3,125
Direct Registered Offering
Offering cost	81	0	0
At The Market Offering Program
Offering cost	1,147	0	0
Series C Convertible Preferred Stock
Issuance cost	$ 0	$ 0	$ 221

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
CASH FLOWS FROM OPERATING ACTIVITIES:
Net loss	$ (72,176)	$ (50,636)	$ (44,995)
Adjustments to reconcile net loss to net cash used in operating activities:
Depreciation and amortization	2,197	1,708	1,256
Stock-based compensation	5,319	2,907	1,066
Accretion on asset retirement obligation	40	36	8
Change in fair value of warrant liability	16,598	(3)	(45)
Loss on disposal of property and equipment	9	358	12
Inventory lower of cost and market adjustment	911	1,939	2,578
Amortization of debt discount and interest accrual	3,321	2,629	1,129
Write-off of deferred offering cost	0	0	2,920
Changes in operating assets and liabilities:
Accounts receivable	(16,126)	(3,370)	74
Inventory	(12,329)	(2,065)	(2,413)
Deposits on purchased inventory	(4,521)	1,414	(1,138)
Deferred cost of revenue	(9,787)	4,873	(4,070)
Prepaid expenses and other assets	(2,044)	(1,633)	(733)
Accounts payable	6,309	381	(2,053)
Notes payable	0	0	(240)
Accrued expenses and other long-term liabilities	850	2,197	1,532
Customer deposits and deferred revenue	11,376	11,109	5,263
Net cash used in operating activities	(70,053)	(28,156)	(39,849)
CASH FLOWS FROM INVESTING ACTIVITIES:
Purchase of property and equipment	(2,163)	(7,031)	(4,151)
Purchase of intangible and other assets	0	(12)	(104)
Change in restricted cash balance	0	(200)	110
Net cash used in investing activities	(2,163)	(7,243)	(4,145)
CASH FLOWS FROM FINANCING ACTIVITIES:
Proceeds from issuance of convertible preferred stock, net	0	0	15,729
Proceeds from draw down of long-term debt	0	15,000	30,000
Payment of debt issuance cost	0	(18)	(1,132)
Payments of long-term debt	0	0	(15,000)
Proceeds from common stock private placement, gross	26,100	13,750	29,447
Payments of costs related to the initial public offering	0	0	(2,728)
Proceeds from the exercise of stock options	665	539	24
Proceeds from the exercise of warrants	103	0	0
Net cash provided by financing activities	115,407	28,930	53,532
NET INCREASE (DECREASE) IN CASH	43,191	(6,469)	9,538
CASH AND CASH EQUIVALENTS — BEGINNING OF PERIOD	14,198	20,667	11,129
CASH AND CASH EQUIVALENTS — END OF PERIOD	57,389	14,198	20,667
SUPPLEMENTAL DISCLOSURE OF CASH FLOW INFORMATION:
Cash paid for interest	3,925	3,310	2,332
Cash paid for taxes	1	0	1
SUPPLEMENTAL NON-CASH INVESTING AND FINANCING ACTIVITIES:
Fair value of common stock warrants issued to placement agents as payment for service	0	0	316
Fair value of common stock warrants reclassed from liability to additional paid-in capital upon exercise	274	0	0
Transfer of property and equipment from inventory	125	117	0
Purchase of property and equipment in accounts payable and accrued expenses	96	193	1,136
Offering costs included in accounts payable and accrued expenses	0	189	0
Conversion of convertible preferred stock warrants into common stock warrants in connection with the Merger	0	0	160,839
Asset retirement obligation	0	0	258
Conversion of convertible preferred stock warrants into common stock warrants	0	0	93
Private Placement
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of offering costs related to common stock issuance	(300)	(341)	(2,808)
At The Market Offering Program
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of offering costs related to common stock issuance	(1,147)	0	0
Proceeds from offering of common stock, gross	40,126	0	0
Direct Registered Offering
CASH FLOWS FROM FINANCING ACTIVITIES:
Payment of offering costs related to common stock issuance	(81)	0	0
Proceeds from offering of common stock, gross	$ 49,941	$ 0	$ 0

Background and Organization

Background and Organization	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Background and Organization	1. Background and Organization On July 23, 2015, ViewRay, Inc. (f/k/a Mirax Corp.), or the Company, and ViewRay Technologies, Inc. (f/k/a ViewRay Incorporated), consummated an Agreement and Plan of Merger and Reorganization, or Merger Agreement. Pursuant to the Merger Agreement, the stockholders of ViewRay Technologies, Inc. contributed all of their equity interests to the Company for shares of the Company’s common stock and merged with the Company’s subsidiary, which resulted in ViewRay Technologies, Inc. becoming a wholly-owned subsidiary of the Company, or the Merger. Refer to Note 3 for further information on the Merger. ViewRay, Inc. and its wholly-owned subsidiary ViewRay Technologies, Inc., designs, manufactures and markets the MRIdian system, an MRI-guided radiation therapy system to image and treat cancer patients simultaneously. Since inception, ViewRay Technologies, Inc. has devoted substantially all of its efforts towards research and development, initial selling and marketing activities, raising capital and the manufacturing and shipment of MRIdian systems. In May 2012, ViewRay Technologies, Inc. was granted clearance from the FDA, to sell MRIdian with Cobalt-60. In November 2013, ViewRay Technologies, Inc. received its first clinical acceptance of a MRIdian with Cobalt-60 at a customer site, and the first patient was treated with that system in January 2014. ViewRay Technologies, Inc. has had the right to affix the CE mark to MRIdian with Cobalt-60 in the European Economic Area since November 2014. In September 2016, the Company received the right to affix the CE mark to MRIdian Linac in the EEA, and in February 2017, the Company received 510(k) clearance from the FDA to market the MRIdian Linac system. The Company’s consolidated financial statements have been prepared on the basis of the Company continuing as a going concern for a reasonable period of time. The Company’s principal sources of liquidity are cash flows from public and private shares offerings and available borrowings under its Term Loan agreement. These have historically been sufficient to meet working capital needs, capital expenditures, and debt service obligations. During the year ended December 31, 2017, the Company incurred a net loss from operations of $72.2 million and used cash from operations of $70.1 million. The Company believes that its existing cash balance of $57.4 million as of December 31, 2017, and the aggregate $59.1 million of proceeds from the February equity financing (see Note 20), are sufficient to provide liquidity to fund its operations for at least the next 12 months.

Summary of Significant Accounti

Summary of Significant Accounting Policies	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	2. Summary of Significant Accounting Policies Basis of Presentation The consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States, or GAAP, and pursuant to the rules and regulation of the Securities and Exchanges Commission, or SEC. The consolidated financial statements include the accounts of ViewRay, Inc. and its wholly-owned subsidiary, ViewRay Technologies, Inc. All inter-company accounts and transactions have been eliminated in consolidation. Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the consolidated financial statements and accompanying notes. Such estimates include, but are not limited to, allocation of revenue to its multiple deliverable elements, inventory write-downs to reflect net realizable value, assumptions used in the valuation of stock-based awards and warrant liability, and valuation allowances against deferred tax assets. Actual results could differ from those estimates. Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. The Company deposits its cash primarily in checking and money market accounts. Restricted Cash At December 31, 2017 and 2016, the Company had an aggregate of $0.9 million of outstanding letters of credit related to its operating leases and its contractual obligations with distributors and customers. The letters of credit are collateralized by a restricted cash deposit account, which is presented as part of noncurrent assets on the balance sheets because the Company is not certain when the restriction will be lifted on the collateralized letters of credit. At December 31, 2017, and 2016, no amounts were drawn on the letters of credit. The restricted cash balance as of December 31, 2017 also includes $0.2 million collateral for a credit card account. Concentration of Credit Risk, Other Risks and Uncertainties Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents and accounts receivable. Cash and cash equivalents are deposited in checking and money market accounts with various financial institutions. At times, cash balances may be in excess of the amounts insured by the Federal Deposit Insurance Corporation. Management believes the financial risk associated with these balances is minimal and has not experienced any losses to date. The Company performs periodic credit evaluations of its customers’ financial condition and generally requires deposits from its customers. The Company’s accounts receivable was derived from billings to customers. The Company’s customers representing greater than 10% of accounts receivable and revenue for the periods presented were as follows: Revenue Accounts Receivables Year Ended December 31, December 31, Customers 2017 2016 2015 2017 2016 Customer A 17% Customer B 17% Customer C 16% 48% Customer D 16% 24% Customer E 14% 16% Customer F 10% Customer G 36% Customer H 47% 49% Customer I 25% Customer J 23% 41% Customer K 43% The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, rapid technological change, continued acceptance of MRIdian, competition from substitute products and larger companies, protection of proprietary technology, ability to maintain distributor relationships and dependence on key individuals. Furthermore, new products to be developed by the Company require approval from the FDA or other international regulatory agencies prior to commercial sales. There can be no assurance that the Company’s future products will receive the necessary clearances. The Company relies on a concentrated number of suppliers to manufacture essentially all of the components used in MRIdian. The Company’s suppliers may encounter problems during manufacturing due to a variety of reasons, including failure to comply with applicable regulations, including the FDA’s Quality System Regulation, equipment malfunction and environmental factors, any of which could delay or impede our ability to meet demand. Accounts Receivables and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount, net of any allowance for doubtful accounts, and do not bear interest. The allowance for doubtful accounts, if any, is based on the assessment of the collectability of customer accounts. Based on the specific customers and the current economic conditions, there was no allowance for doubtful accounts recorded at December 31, 2017 and 2016. Fair Value of Financial Instruments Financial instruments consist of cash and cash equivalents, accounts receivable, restricted cash, prepaid expenses and other current assets, accounts payable, accrued liabilities, warrant liability and long-term debt. Cash equivalents are stated at amortized cost, which approximates fair value at the balance sheet dates, due to the short period of time to maturity. Accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities are stated at their carrying value, which approximates fair value due to the short time to the expected receipt or payment date. The warrant liability is carried at fair value. The carrying amount of the Company’s long-term debt approximates fair value as the stated interest rate approximates market rates currently available to the Company. Inventory and Deposits on Purchased Inventory Inventory consists of purchased components for assembling MRIdian systems and other direct and indirect costs associated with MRIdian system installation. Inventory is stated at the lower of cost (on a weighted average cost basis) or market value. All inventories expected to be placed in service during the normal operating cycle of the Company for the delivery and assembly of MRIdian systems, including items expected to be on hand for more than one year, are classified as current assets. The Company reduces the carrying value of its inventory for the difference between cost and net realizable value and records a charge to cost of product revenues for the amount required to reduce the carrying value of inventory to net realizable value. The Company recorded an inventory lower of cost and market adjustment of $0.9 million, $1.9 million and $2.6 million during the years ended December 31, 2017, 2016 and 2015, respectively. The Company records inventory items which have been paid for but not yet received and title has not yet transferred to the Company as deposits on purchased inventory. Deposits on purchased inventory are included within current assets as the related inventory items are expected to be received and used in MRIdian systems within the Company’s normal operating cycle. The Company assesses the recoverability of deposits on purchased inventory based on credit assessments of the vendors and their history supplying these assets. At December 31, 2017, the Company did not have any instances whereby deposits for purchased inventory were written off or the purchased inventory was not delivered. Shipping and Handling Costs Shipping and handling costs for product shipments to customers are included in cost of product revenue. Shipping and handling costs incurred for inventory purchases are capitalized in inventory and expensed in cost of product revenue. These costs are not passed on to customers. Property and Equipment Property and equipment are recorded at cost. Depreciation is computed over estimated useful lives, ranging from two to 15 years, of the related assets using the straight-line method. Acquired software is recorded at cost. Amortization of acquired software generally occurs over three years using the straight-line method. Leasehold improvements are amortized on a straight-line basis over the shorter of the useful life or term of the lease. Demonstration units, which are the Company products used for demonstration purpose for customers and/or potential customers, and generally not intended to be sold, are amortized by the straight-line method. Upon retirement or sale, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is recorded to general and administrative expense in the accompanying statements of operations and comprehensive loss. Routine expenditures for maintenance and repairs are expensed as incurred. Depreciation and amortization periods for property and equipment are as follows: Property and Equipment Estimated Useful Life Prototype 2 – 10 years Machinery and equipment 5 – 15 years Furniture and fixture 5 – 10 years Software 3 years Leasehold improvements Lesser of estimated useful life or remaining lease term Asset Retirement Obligation In connection with certain lease agreements entered into in October 2015, the Company has a legal requirement to remove long-lived assets constructed on leased property and to restore the leased property to its original condition. The Company records the fair value of the liability for a legal obligation to retire an asset in the period in which the obligation is incurred if a reasonable estimate of fair value can be made. The Company measures the fair value of the asset retirement obligation based upon the present value of the expected future payments, and recognized asset retirement obligation of $250,000 at inception. The liability is accreted to its present value each period and the capitalized cost is depreciated over the remaining lease term. Accretion expense is calculated by applying the effective interest rate to the carrying amount of the liability at the beginning of each period. The effective interest rate is the credit-adjusted risk-free rate applied when the liability was initially measured and recognized. At December 31, 2017, the Company had outstanding asset retirement obligations of $334,000, which was included in other long-term liabilities in the accompanying consolidated balance sheets. For the years ended December 31, 2017, 2016 and 2015, the Company recognized accretion expenses of $40,000, $36,000 and $8,000 in the accompanying statements of operations and comprehensive loss. Intangible Assets Intangible assets consist primarily of patents and license acquisition costs associated with certain technology components incorporated into the Company’s MRIdian systems. The Company capitalizes the cost and amortizes it on a straight-line basis over the estimated useful lives, which is generally three years for license cost and five to seven years for patents. Impairment of Long-Lived Assets The Company reviews the recoverability of long-lived assets, including equipment, leasehold improvements, software and intangible assets when events or changes in circumstances occur that indicate that the carrying value of the asset may not be recoverable. The assessment of possible impairment is based on the ability to recover the carrying value of the assets from the expected future cash flows (undiscounted and without interest charge) of the related operations. If these cash flows are less than the carrying value of such assets, an impairment loss for the difference between the estimated fair value and carrying value is recorded. There was no impairment loss recognized during the years ended December 31, 2017, 2016 and 2015. Deferred Offering Costs ViewRay Technologies, Inc. capitalized qualified legal, accounting and other direct costs related to its efforts to raise capital through a public sale of its common stock in its planned IPO. These costs were recorded in deferred offering costs in the accompanying balance sheets Comprehensive Loss Comprehensive loss is the change in equity of a company during a period from transactions and other events and circumstances, excluding transactions resulting from investment owners and distribution to owners. For the periods presented, comprehensive loss did not differ from net loss. Revenue Recognition The Company derives revenue primarily from the sale of the systems and related services, which are sales of MRIdian, as well as support and maintenance services on sold systems. In all sales arrangements, the Company recognizes revenues when there is persuasive evidence of an arrangement, the fee is fixed or determinable, collection of the fee is reasonably assured and delivery has occurred. For sales of MRIdian systems that the Company is required to install at the customer site, product revenue is recognized upon receipt of customer acceptance. For sales of MRIdian systems that the Company is not responsible for installation, product revenue is recognized when the entire system is delivered and title and risk of loss are transferred to the customer. For sales of the related support and maintenance services, the Company recognizes service revenue on a straight-line basis over the service contract term, which is typically 12 months. Multiple Elements Based on the nature of the Company’s business, it frequently enters into sales arrangements with customers that contain multiple elements or deliverables. The principal deliverables consist of (i) sale of MRIdian systems, which generally includes installation, site preparation and software, and (ii) product support, which includes extended service and maintenance. The Company determines selling prices of each deliverable using vendor specific objective evidence, or VSOE, if it exists, or third-party evidence, or TPE. If neither VSOE nor TPE exists for a deliverable, the Company uses best estimated selling price, or BESP. The Company allocates revenue to each standalone deliverable using the relative fair values for each deliverable as determined by BESP. The Company regularly reviews VSOE, TPE and BESP for all of its MRIdian systems and services. Product Revenue Product revenue is derived primarily from the sales of MRIdian. The system contains both software and non-software components that together deliver essential functionality. However, because MRIdian includes hardware products as well as software components that function together with the hardware components to deliver MRIdian’s essential functionality, the revenue from the sale of MRIdian systems does not fall within the scope of the software revenue recognition rules. The Company’s customer contracts generally call for on-site assembly of the system components and system integration. Once the system installation is completed, the Company performs a detailed demonstration with the customer showing that MRIdian meets the standard product specifications. After successful demonstration, the customer signs a document indicating customer’s acceptance. For sales of MRIdian systems that the Company is required to install at the customer site, revenue recognition occurs when the customer acknowledges that the system operates in accordance with standard product specifications, the customer accepts the installed unit and title and risk of loss are transferred to the customer. Certain customer contracts with distributors do not require installation at the customer site, and the distributors typically have its own or engage a qualifying third-party certified technician to perform the installation. For sales of MRIdian systems when the Company is not responsible for installation, revenue recognition occurs when the entire system is delivered and title and risk of loss are transferred to the customer. All contracts include customer deposits upon signing of the agreement with final payment generally due upon customer acceptance. Service Revenue Service revenue is derived primarily from maintenance services. Service revenue is recognized ratably over the service period. Distribution Rights Revenue The Company entered into a distribution agreement with Itochu Corporation pursuant to which it appointed Itochu as its exclusive distributor for the promotion, sale and delivery of MRIdian products within Japan. In consideration of the exclusive distribution rights granted, the Company received $4.0 million which was recorded as deferred revenue and starting in August 2016 was recognized as distribution rights revenue on a straight-line basis over the remaining term of the distribution agreement of approximately 8.5 years . Customer Deposits Customer deposits represent payments received in advance of system installation. For domestic sales, advance payments received prior to inventory shipments and customer acceptance are recorded as customer deposits. For international sales, advance payments are initially recorded as customer deposits and are subsequently reclassified to deferred revenue upon inventory shipment when the title and risk of loss of inventory items transfer to customers. All customer deposits, including those that are expected to be a deposit for more than one year, are classified as current liabilities based on consideration of the Company’s normal operating cycle (the time between acquisition of the inventory components and the final cash collection from customers on these inventory components) which is in excess of one year. Deferred Revenue and Deferred Cost of Revenue Deferred revenue consists of deferred product revenue and deferred service revenue. Deferred product revenue arises from timing differences between the fulfillment of other contract deliverables and satisfaction of all revenue recognition criteria consistent with the Company’s revenue recognition policy. Deferred service revenue results from the advance billing for services to be delivered over a period of time. Deferred revenues expected to be realized within one year are classified as current liabilities. Deferred cost of revenue consists of cost for inventory items that have been shipped with title and risk of loss transferred to the customer but the customer acceptance has not been received. Deferred cost of revenue is included as part of current assets as the corresponding deferred product revenue is expected to be realized within one year. The inventories recorded in deferred cost of revenue are also included in the inventory lower of cost or market analysis. At December 31, 2017 and 2016, no reserve was required for deferred cost of revenue. Research and Development Costs Expenditures, including payroll, contractor expenses and supplies, for research and development of products and manufacturing processes are expensed as incurred. Software development costs incurred subsequent to establishing technological feasibility are capitalized through the general release of MRIdian systems that contain the embedded software elements. Technological feasibility is demonstrated by the completion of a working model. The Company has not capitalized any software development costs at December 31, 2017 or 2016, since the costs incurred subsequent to achieving technological feasibility and completing the research and development for the software components were immaterial. Stock-Based Compensation The Company uses the Black-Scholes option-pricing model as the method for estimating the fair value of stock options. The Black-Scholes option-pricing model requires the use of highly subjective and complex assumptions that determine the fair value of share-based awards, including the options’ expected term and the price volatility of the underlying stock Medical Device Excise Tax Medical Device Excise Tax, or MDET, Section 4191 of the Internal Revenue Code enacted by the Health Care and Education Reconciliation Act of 2010, in conjunction with the Patient Protection and Affordable Care Act, established a 2.3% excise tax on medical devices sold domestically which, due to subsequent legislative amendments, was suspended from January 1, 2016 to December 31, 2017. MDET was suspended for another two years after the stopgap bill was signed by the President in January 2018 The Company included MDET in cost of product revenue during the year ended December 31, 2015, net of amounts directly billed to the customer for this tax, if any. Deferred Commissions Deferred commissions are the direct and incremental costs directly associated with the MRIdian system contracts with customers, which primarily consist of sales commissions to our direct sales force. The commissions are deferred and expensed in proportion to the revenue recognized upon the acceptance of the MRIdian system. At December 31, 2017 and 2016, the Company had $3.5 million and $2.6 million deferred commissions recorded as part of prepaid expenses and other current assets on the accompanying consolidated balance sheets. Income Taxes The Company uses the asset and liability method of accounting for income taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Deferred tax expense or benefit is the result of changes in the deferred tax assets and liabilities. Valuation allowances are established when necessary to reduce deferred tax assets where, based upon the available evidence, management concludes that it is more-likely-than not that the deferred tax assets will not be realized. Because of the uncertainty of the realization of the deferred tax assets, the Company has recorded a full valuation allowance against its net deferred tax assets. In evaluating the ability to recover its deferred income tax assets, the Company considers all available positive and negative evidence, including its operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. In the event the Company was to determine that it would be able to realize its deferred income tax assets in the future in excess of their net recorded amount, it would make an adjustment to the valuation allowance which would reduce the provision for income taxes. Reserves are provided for tax benefits for which realization is uncertain. Such benefits are only recognized when the underlying tax position is considered more likely than not to be sustained on examination by a taxing authority, assuming they possess full knowledge of the position and facts. It is the Company’s policy to include any penalties and interest related to income taxes in its income tax provision; however, the Company currently has no penalties or interest related to income taxes. The earliest year that the Company is subject to examination is the year ended December 31, 2004. Warrant Liability Convertible Preferred Stock Warrant Liability The Company’s warrant to purchase convertible preferred stock was classified as a liability on the consolidated balance sheets at fair value upon issuance because the warrant is exercisable for contingently redeemable preferred stock which is classified outside of stockholders’ equity (deficit). The warrant was subject to re-measurement to fair value at each balance sheet date, and any change in fair value was recognized in the consolidated statements of operations and comprehensive loss as other expense, net. In July 2015, upon the Merger of the Company and ViewRay Technologies, Inc., and the Private Placement, the convertible preferred stock warrants were converted into warrants to purchase the Company’s common stock, and the fair value of the preferred stock warrant liability was reclassified to additional paid-in capital. Common Stock Warrant Liability Certain warrants to purchase common stock provide for cash settlement in the event of change in control, and are classified as liabilities on the balance sheets at fair value upon issuance (see Note 14). These warrants are subject to re-measurement to fair value at each balance sheet date, and any change in fair value are recognized in the consolidated statements of operations and comprehensive loss as other expense, net. Upon exercise or expiration of the warrants, the related warrant liability will be reclassified to additional paid-in capital. Net Loss per Share The Company’s basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. Contingently issuable shares are included in the computation of basic net loss per share as of the date that all necessary conditions have been satisfied and issuance of the shares is no longer contingent. The diluted net loss per share is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, stock options, restricted stock units and warrants to purchase common stock are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share as their effect is anti-dilutive. Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) The Company will adopt Topic 606 on January 1, 2018 using the full retrospective method which requires the Company to restate each prior reporting period presented. Based on the nature of its sales arrangements, the Company does not believe the adoption of the new standards will have a material impact on the amount or timing of its revenue recognition, and the Company’s product revenue, service revenue and distribution rights revenue will remain substantially unchanged. As a result, the adoption of the new standards will have no material impact on the Company’s prior period financial statements. The Company expects to update the related disclosures upon adoption of the new standards in In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) As disclosed in Note 7, future minimum payments under noncancelable operating leases are approximately $2.2 million. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, Statement of Cash Flows (Topic 230): Restricted Cash, In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting Recently Adopted Accounting Pronouncements In July 2015, the FASB issued ASU No. 2015-11, Simplifying the Measurement of Inventory In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation (Topic 718 ): Improvements to Employee Share-Based Payment Accounting

Merger

Merger	12 Months Ended
	Dec. 31, 2017
Business Combinations [Abstract]
Merger	3. Merger On July 23, 2015, ViewRay, Inc. (f/k/a Mirax Corp.), or the Company, and ViewRay Technologies, Inc. (f/k/a ViewRay Incorporated), consummated an Agreement and Plan of Merger and Reorganization, or Merger Agreement. Pursuant to the Merger Agreement, the stockholders of ViewRay Technologies, Inc. contributed all of their equity interests to the Company for shares of the Company’s common stock and merged with the Company’s subsidiary, which resulted in ViewRay Technologies, Inc. becoming a wholly-owned subsidiary of the Company, or the Merger. Effective as of July 23, 2015, the Company amended and restated its Certificate of Incorporation to increase its authorized common stock to 300,000,000 shares and 10,000,000 shares of “blank check” preferred stock, par value of $0.01 per share. Upon the closing of the Merger, under the terms of the Split-Off Agreement, dated July 23, 2015 among the Company, ViewRay Technologies, Inc. and Vesuvius Acquisition Sub, Inc., the acquisition subsidiary of the Company, or the Split-Off Agreement, and a general release agreement dated July 23, 2015, or the General Release Agreement, the Company transferred all of its pre-Merger operating assets and liabilities to wholly- owned special-purpose subsidiary incorporated in Nevada, Vesuvius Acquisition Sub, Inc. or the Split-Off Subsidiary. Thereafter, the Company transferred all of the outstanding shares of capital stock of the Split-Off Subsidiary to certain pre-Merger insiders of the Company in exchange for the surrender and cancellation of shares of the Company’s common stock held by such persons. Together with the Merger, on 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. At the closing of the Merger, the Company conducted a private placement offering, or the Private Placement, of its securities for $26.3 million, net of offering cost, through the sale of 5,884,504 shares of the common stock of the surviving corporation, at an offering price of $5.00 per share. Investors in ViewRay Technologies, Inc. purchased $17.0 million of shares in the Private Placement. Certain shareholders of the Company retained, after giving effect to the Split-Off, 1,000,005 shares of the common stock of the surviving corporation upon the Private Placement. The former stockholders of ViewRay Technologies Inc. collectively own approximately 90.9% of the outstanding shares of the Company’s common stock. Immediately following the closing of the Merger, the Company’s outstanding shares of common stock (on a fully diluted basis) were owned as follows: • Former holders of the ViewRay Technologies, Inc.’s capital stock hold an aggregate of 34,715,582 shares of the Company’s common stock, or approximately 72.7% on a fully diluted basis; • The Private Placement, resulted in an aggregate of 5,884,504 shares of the Company’s common stock, consisting of 3,400,003 shares held by ViewRay Technologies, Inc. shareholders and 2,484,501 shares issued to new shareholders, or together approximately 12.3% on a fully diluted basis; • 128,231 shares of ViewRay Technologies, Inc.’s preferred stock warrants were converted to the Company’s common stock warrant, or approximately 0.3% on a fully diluted basis; • 198,760 shares of common stock issued as warrants to placement agents as payment for services provided, or approximately 0.4% on a fully diluted basis; • Holders of the Company’s common stock prior to the closing of the Merger hold an aggregate of 1,000,005 shares of the Company’s common stock, or approximately 2.1% on a fully diluted basis; and • 9,225,397 shares of common stock are reserved for issuance under the 2008 Stock Incentive Plan, or the 2008 Plan, and the 2015 Equity Incentive Plan of ViewRay, or the 2015 Plan, collectively representing approximately 19.3% on a fully diluted basis. Upon closing, 1,507,147 options to purchase shares of the Company’s common stock are granted to employees under the 2015 Plan. In addition, the Board of Directors of the Company has adopted a 285,621-share reserve under the 2015 ESPP. The Merger was accounted for as a reverse-merger and recapitalization. ViewRay Technologies, Inc. was the acquirer for financial reporting purposes, and ViewRay, Inc. was the acquired company under the acquisition method of accounting in accordance with FASB ASC Topic 805, Business Combination. Consequently, the assets, liabilities and operations that will be reflected in the historical consolidated financial statements prior to the Merger will be those of ViewRay Technologies, Inc. and will be recorded at the historical cost basis, and the consolidated financial statements after completion of the Merger will include the assets, liabilities and results of operations of ViewRay Technologies, Inc. up to the day prior to the closing of the Merger and the assets, liabilities and results of operations of the combined company from and after the closing date of the Merger.

Balance Sheet Components

Balance Sheet Components	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Balance Sheet Components	4. Balance Sheet Components Property and Equipment Property and equipment consisted of the following (in thousands): December 31, 2017 2016 Prototype $ 11,929 $ 6,405 Machine and equipment 7,831 6,057 Leasehold improvements 4,438 4,371 Furniture and fixtures 558 368 Software 1,142 1,028 Construction in progress - 5,498 Property and equipment, gross 25,898 23,727 Less: accumulated depreciation and amortization (14,334 ) (12,167 ) Property and equipment, net $ 11,564 $ 11,560 Depreciation and amortization expense related to property and equipment was $2.2 million, $1.6 million and $1.1 million during the years ended December 31, 2017, 2016 and 2015, respectively. Intangible Assets Intangible assets consisted of the following (in thousands): December 31, 2017 2016 License cost $ 512 $ 512 Patents 104 104 Intangible assets, gross 616 616 Accumulated amortization (538 ) (519 ) Intangible assets, net $ 78 $ 97 Intangible amortization expense was $19 thousand, $115 thousand and $168 thousand during the years ended December 31, 2017, 2016 and 2015, respectively, which were recorded in general and administrative expenses in the consolidated statements of operations and comprehensive loss. At December 31, 2017, the estimated future amortization expense of purchased intangible assets was as follows (in thousands): Year Ended December 31, Estimated Amortization Expense 2018 $ 19 2019 19 2020 19 2021 10 2022 3 Thereafter 8 Total amortization expense $ 78 Accrued Liabilities Accrued liabilities consisted of the following (in thousands): December 31, 2017 2016 Accrued payroll and related benefits $ 3,944 $ 4,274 Accrued accounts payable 2,671 1,202 Tax payable 149 13 Accrued legal and accounting 322 509 Other 121 336 Total accrued liabilities $ 7,207 $ 6,334 Deferred Revenue Deferred revenue consisted of the following (in thousands): December 31, 2017 2016 Deferred revenue: Product $ 18,861 $ 5,050 Services 1,182 1,561 Distribution rights 3,346 3,822 Total deferred revenue 23,389 10,433 Less: current portion of deferred revenue (20,151 ) (6,515 ) Noncurrent portion of deferred revenue $ 3,238 $ 3,918

Fair Value of Financial Instrum

Fair Value of Financial Instruments	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Fair Value of Financial Instruments	5. Fair Value of Financial Instruments Assets and liabilities recorded at fair value on a recurring basis in the balance sheets are categorized based upon the level of judgment associated with the inputs used to measure their fair values. Fair value is defined as the exchange price that would be received for an asset or paid to transfer a liability (an exit price) in the principal or most advantageous market for the asset or liability in an orderly transaction between market participants on the measurement date. Valuation techniques used to measure fair value must maximize the use of observable inputs and minimize the use of unobservable inputs. The standard describes a fair value hierarchy based on three levels of inputs, of which the first two are considered observable and the last unobservable, that may be used to measure fair value which are the following: Level 1—Quoted prices in active markets for identical assets or liabilities. Level 2—Inputs other than Level 1 that are observable, either directly or indirectly, such as quoted prices for similar assets or liabilities; quoted prices in markets that are not active; or other inputs that are observable or can be corroborated by observable market data for substantially the full term of the assets or liabilities. Level 3—Unobservable inputs that are supported by little or no market activity and that are significant to the fair value of the assets or liabilities. The assets’ or liabilities’ fair value measurement level within the fair value hierarchy is based on the lowest level of any input that is significant to the fair value measurement. The Company’s financial instruments that are carried at fair value mainly consist of Level 1 assets and Level 3 liabilities. Level 1 assets include highly liquid bank deposits and money market funds, which were not material at December 31, 2017 or 2016. Level 3 liabilities that are measured on a recurring basis consists of convertible preferred stock warrants and common stock warrants. Preferred stock warrant and common stock warrant liabilities are valued using the Black-Scholes option-pricing model. Generally, increases (decreases) in the fair value of the underlying stock, estimated term and volatility would result in a directionally similar impact to the fair value of the warrant (see Note 13). The convertible preferred stock warrants were issued in December 2013 and were converted into warrants to purchase common stock upon the Merger of the Company and ViewRay Technologies, Inc. The aggregate fair value of these warrants upon the closing of the Merger is $93 thousand which was reclassified from liabilities to additional paid-in-capital, and the Company no longer recorded change in fair value adjustments in relation to convertible preferred stock warrants. The Company’s common stock warrants liabilities consist of the 2017 and 2016 Placement Warrants, as described in Note 13. The 2016 Placement Warrants were issued in August and September 2016, and the 2017 Placement Warrants were issued in January 2017. In December 2017, 25,014 shares of 2016 Placement Warrants and 9,389 shares of 2017 Placement Warrants were exercised and the aggregate fair value of these warrants upon exercise of $274 thousand was reclassified from liabilities to additional paid-in-capital. At December 31, 2017, 1,355,641 shares of 2016 Placement Warrants and 1,711,123 shares of 2017 Placement Warrants were outstanding. The gains and losses from re-measurement of Level 3 financial liabilities are recorded as part of other income (expense), net in the consolidated statements of operations and comprehensive loss. During the year ended December 31, 2017 and 2016, the Company recorded a loss of $16.6 million and a gain of $3 thousand, respectively, related to the change in fair value of the 2016 and 2017 Placement Warrants. There have been no transfers between Level 1, Level 2 and Level 3 in any periods presented. The following table sets forth the fair value of the Company’s financial liabilities by level within the fair value hierarchy (in thousands): At December 31, 2017 Level 1 Level 2 Level 3 Total 2017 Placement Warrants Liability $ — $ — $ 12,487 $ 12,487 2016 Placement Warrants Liability — — 9,933 9,933 Total Warrant Liability $ — $ — $ 22,420 $ 22,420 At December 31, 2016 Level 1 Level 2 Level 3 Total 2016 Placement Warrants Liability $ — $ — $ 2,723 $ 2,723 The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands): Year Ended December 31, 2017 2016 2015 Fair value, beginning of period $ 2,723 $ — $ 138 Issuance of 2017 Placement Warrants 3,373 — — Issuance of 2016 Placement Warrants — 2,726 — Change in fair value of Level 3 financial liabilities 16,598 (3 ) (45 ) Conversion of convertible preferred stock warrants to common stock warrants — — (93 ) Fair value of 2017 Placement Warrants at exercise (74 ) — — Fair value of 2016 Placement Warrants at exercise (200 ) — — Fair value, end of period $ 22,420 $ 2,723 $ —

Debt

Debt	12 Months Ended
	Dec. 31, 2017
Debt Instruments [Abstract]
Debt	6. Debt Hercules Term Loan In December 2013, ViewRay Technologies, Inc. entered into a Loan and Security Agreement, or the Hercules Term Loan, with Hercules Technology Growth Capital, Inc. and Hercules Technology III, L.P., or together, Hercules, for $15.0 million that was outstanding at December 31, 2014. Borrowings under the Hercules Term Loan bear cash interest at the greater of the annual prime rate plus 7.0% or 10.25%. In addition, borrowings under the Hercules Term Loan bear deferred payment in-kind interest at 1.5% per annum. Interest only payments began in January 2014, with monthly principal and interest payments beginning on January 1, 2015 and the entire balance of the Hercules Term Loan are to be paid in full by the June 1, 2017 maturity date. The Hercules Term Loan is subject to a prepayment penalty of 5% on the outstanding balance during the first 12 months following the funding of the loan and 1% on the outstanding balance thereafter until maturity. The Hercules Term Loan was issued at a discount of $466 thousand, which was amortized to interest expense during the life of the loan using the effective interest method. The discount included the fair value of a convertible preferred stock warrant that was issued with the Hercules Term Loan, as discussed in the following paragraph, and the related transaction costs. The Hercules Term Loan is collateralized by essentially all the assets of ViewRay Technologies, Inc. and limits its ability with respect to additional indebtedness, investments or dividends, among other things, subject to customary exceptions. In connection with the issuance of the Hercules Term Loan, ViewRay Technologies, Inc. entered into a Warrant Agreement with Hercules to issue a fully vested and exercisable warrant to purchase 128,231 shares of Series C convertible preferred stock with an exercise price of $5.84 per share. The warrant is exercisable any time before the later of 10 years from issuance or five years after an IPO. The warrant provides for anti-dilution rights on the Series C convertible preferred stock, which includes one-time down-round protection. The fair value of the warrant upon issuance of $158 thousand was recorded as convertible preferred stock warrant liability and a discount to the carrying value of the Hercules Term Loan. The fair value of the warrant at the time of issuance was estimated using the Black-Scholes option-pricing model with the assumptions: expected term of two years, expected volatility of 30%, risk-free interest rate of 0.4% and expected dividend yield of 0%. The convertible preferred stock warrants were converted into warrants to purchase the Company’s common stock upon the consummation of the Merger in July 2015 as disclosed in Notes 1 and 5. See Note 14 for assumptions used to estimate the fair value of convertible preferred stock warrant liability upon conversion into warrants to purchase common stock on July 23, 2015. In June 2015, ViewRay Technologies, Inc. paid off in full the outstanding balances on Hercules Term Loan, including the related interest and other penalty fee, using part of the proceeds received from the CRG Term Loan discussed below. CRG Term Loan In June 2015, ViewRay Technologies, Inc. entered into a Term Loan Agreement, or the CRG Term Loan, with Capital Royalty Partners II L.P., Capital Royalty Partners II – Parallel Fund “A” L.P., Capital Royalty Partners II (Cayman) L.P. and Parallel Investment Opportunities Partners II L.P. or together with their successors by assignment, CRG, for up to $50.0 million of which $30.0 million was made available to the Company upon closing with the remaining $20.0 million available on or before June 26, 2016 at its option upon the occurrence of either (i) an initial public offering of its common stock on a nationally recognized securities exchange that raises a minimum of $40.0 million in net cash proceeds with a minimum of $120.0 million post money valuation, or Qualifying IPO, or (ii) achievement of a minimum of $25.0 million gross revenue from the sales of the MRIdian system during any consecutive 12 months before March 31, 2016. The Company drew down the first $30.0 million on the closing date. The CRG Term Loan has a maturity date of June 26, 2020 and bears cash interest at a rate of 12.5% per annum to be paid quarterly during the interest-payment-only period of three years. In April 2017, the CRG Term Loan was amended to allow for interest-payment-only until March 31, 2020. During the interest-payment-only period, the Company has the option to elect to pay only 8% of the 12.5% per annum interest in cash, and the remaining 4.5% of the 12.5% per annum interest as compounded interest, or deferred payment in-kind interest, added to the aggregate principal amount of the CRG Term Loan. Principal payment and any deferred payment in-kind interest will be paid quarterly in equal installments following the end of the interest-payment-only period through maturity date. The CRG Term Loan is subject to a prepayment penalty of 3% on the outstanding balance during the first 12 months following the funding of the loan, 2% on the outstanding balance after year 1 but on or before year 2, 1% on the outstanding balance after year 2 but on or before year 3, and 0% on the outstanding loan if prepaid after year 3 thereafter until maturity. The Term Loan is also subject to a facility fee of 7% based on the sum of the amount drawn and any outstanding payment in-kind interest payable on the maturity date or the date such loan becomes due. All direct financing costs were accounted for as a discount on the CRG Term Loan and will be amortized to interest expense during the life of the loan using the effective interest method. The CRG Term Loan is subject to financial covenants and is collateralized by essentially all assets of the Company and limits its ability with respect to additional indebtedness, investments or dividends, among other things, subject to customary exceptions. 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. The Company achieved the minimum of $15.0 million gross revenue requirement in March 2016 which made the first $15.0 million of the remaining $20.0 million credit facility immediately available for draw down. In May 2016, the Company drew down the additional $15.0 million available amount. 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. The Company did not draw down any amounts under the $5.0 million tranche and it has since expired. 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. The Company did not draw down any amount under the $15.0 million tranche and it has since expired. 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. At December 31, 2017, the Company had $45.0 million in outstanding debt and $4.8 million in deferred payment in- kind interest to CRG, and was in compliance with all financial covenants under the CRG Term Loan. The Company’s scheduled future payment on the CRG Term Loan at December 31, 2017 are as follows (in thousands): Year Ended December 31, 2018 $ 4,108 2019 4,299 2020 62,803 Total future payments 71,210 Less: amount representing interest and end-of-term facility fee (26,210 ) Total principal amount 45,000 Less: unamortized debt discount (496 ) Carrying value of long-term debt 44,504 Less: current portion — Long-term portion $ 44,504

Commitments and Contingencies

Commitments and Contingencies	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	7. Commitments and Contingencies Operating Leases The Company leases office space in Oakwood Village, Ohio and Mountain View, California under non-cancellable operating leases. At December 31, 2017, the future minimum payments for the operating leases are as follows (in thousands): Year Ended December 31, 2018 $ 1,118 2019 1,039 Total future minimum payments $ 2,157 Rent expense incurred under operating leases was $1.3 million in each of the years ended December 31, 2017, 2016 and 2015, respectively. Contingencies The Company is subject to claims and assessments from time to time in the ordinary course of business. The Company records a provision for a liability when it believes that it is both probable that a liability has been incurred and the amount can be reasonably estimated. Significant judgment is required to determine both probability and the estimated amount. In the normal course of business, the Company may become involved in legal proceedings. The Company will accrue a liability for such matters when it is probable that a liability has been incurred and the amount can be reasonably estimated. When only a range of possible loss can be established, the most probable amount in the range is accrued. If no amount within this range is a better estimate than any other amount within the range, the minimum amount in the range is accrued. The accrual for a litigation loss contingency might include, for example, estimates of potential damages, outside legal fees and other directly related costs expected to be incurred. The Company was subject to an arbitration claim that arose in the ordinary course of business at September 30, 2017. This claim was settled in the fourth quarter of fiscal year 2017. At December 31, 2017, the Company was not involved in any material legal proceedings. Purchase Commitments At December 31, 2017 and 2016, the Company had no outstanding firm purchase commitments.

License Agreement

License Agreement	12 Months Ended
	Dec. 31, 2017
Text Block [Abstract]
License Agreement	8. Licensing Agreement In December 2004, ViewRay Technologies, Inc. entered into a licensing agreement with the University of Florida Research Foundation, Inc., or UFRF, whereby UFRF granted the Company a worldwide exclusive license to certain of UFRF’s patents in exchange for 33,652 shares of common stock and a royalty from sales of products developed and sold by the Company utilizing the licensed patents. ViewRay Technologies, Inc. met all of the product development and commercialization milestones at December 31, 2013 and started to make quarterly royalty payments in 2014. Royalty payments are based on 1% of net sales, defined as the amount collected on sales of licensed products and/or licensed processes after deducting trade and/or quantity discounts, credits on returns and allowances, outbound transportation costs paid and sales tax. Minimum quarterly royalty payments of $50 thousand commenced with the quarter ended March 31, 2014 and are payable in advance. Minimum royalties paid in any calendar year will be credited against earned royalties for such calendar year. The royalty payments continue until the earlier of (i) the date that no licensed patents remain enforceable or (ii) the payment of earned royalties, once begun in 2014, cease for more than four consecutive calendars quarters. Royalty expenses based on 1% of net sales were $274.4 thousand, $206 thousand and $49 thousand during the years ended December 31, 2017, 2016 and 2015, respectively, and were recorded as product cost of revenue in the accompanying consolidated statements of operations and comprehensive loss. The minimum royalty payments in excess of 1% of net sales were $25 thousand, $57 thousand and $102 thousand during the years ended December 31, 2017, 2016 and 2015, respectively, and were recorded as general and administrative expenses in the accompanying consolidated statements of operations and comprehensive loss.

Distribution Agreement

Distribution Agreement	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Distribution Agreement	9. Distribution Agreement In December 2014, the Company entered into a distribution agreement with Itochu Corporation, or Itochu, a Japanese entity, pursuant to which the Company appointed Itochu as its exclusive distributor for the sale and delivery of its MRIdian products within Japan. The exclusive distribution agreement has an initial term of 10 years from December 2014, and contains features customary in such distribution agreements. Under this distribution agreement, the Company will supply its products and services to Itochu based upon the Company’s then-current pricing. In consideration of the exclusive distribution rights granted, ltochu agreed to pay a distribution fee of $4.0 million in three installments: (i) the first installment of $1.0 million was due upon execution of the distribution agreement; (ii) the second installment of $1.0 million was due within 10 business days following submission of the application for regulatory approval of the Company’s product to the Japan regulatory authority; and (iii) the final installment of $2.0 million was due within 10 business days following receipt of approval for the Company’s product from the Japanese Ministry of Health, Labor and Welfare. The distribution fee paid by Itochu was refundable if the Company failed to obtain the approval from the Japan regulatory authority before December 31, 2017. The first and second installments of $2.0 million in aggregate were received in December 2014 and December 2015, respectively. In August 2016, the Company received the third and final $2.0 million installment upon the receipt of regulatory approval to market MRIdian in Japan

Equity Financing

Equity Financing	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Equity Financing	10. Equity Financing Private Placements In September 2016, the Company completed the final closing of a private placement offering, or the 2016 Private Placement, through which it sold (i) 4,602,506 shares of its common stock and (ii) warrants that provide the warrant holders the right to purchase 1,380,745 shares of common stock, or the 2016 Placement Warrants, and raised total gross proceeds of $13.8 million. The 2016 Placement Warrants have an exercise price of $2.95 per share, are exercisable at any time at the option of the holder and expire seven years from the date of issuance. In January 2017, the Company completed the final closing of a private placement offering, or the January 2017 Private Placement, through which it sold (i) 8,602,589 shares of its common stock and (ii) warrants that provide the warrant holders the right to purchase 1,720,512 shares of common stock, or the 2017 Placement Warrants, and raised total gross proceeds of $26.1 million. The 2017 Placement Warrants have an exercise price of $3.17 per share, became exercisable in July 2017 and expire in January 2024. Direct Registered Offering In October 2017, the Company completed the final closing of a direct registered offering, or the October 2017 Direct Registered Offering, through which it sold 8,382,643 shares of its common stock and raised total gross proceeds of $50.0 million. At-The-Market Offering of Common Stock In January 2017, the Company filed a shelf registration statement on Form S-3 with the SEC, which included a base prospectus covering the offering, issuance and sale of up to a maximum aggregate offering of $75.0 million of the Company’s common stock, preferred stock, debt securities, warrants, purchase contracts and/or units; and in accordance with Rule 415(a)(4) under the Securities Act FBR acted as sales agent on a best efforts basis and used commercially reasonable efforts to sell on behalf of the Company all of the shares of common stock requested to be sold by the Company, consistent with its normal trading and sales practices, on mutually agreed terms between FBR and the Company. There is no arrangement for funds to be received in any escrow, trust or similar arrangement. In April 2017, the Company agreed to sell up to an additional $25.0 million of the Company’s common stock in accordance with the terms of a sales agreement with FBR and pursuant to an at-the-market offering program in accordance with Rule 415(a)(4) under the Securities Act. FBR is entitled to compensation of up to 3.0% of the gross sales price per share sold. In connection with the sale of the Company’s common stock on the Company’s behalf, FBR is deemed to be an “underwriter” within the meaning of the Securities Act and the compensation of FBR is deemed to be underwriting commissions or discounts. The Company has also agreed to provide indemnification and contribution to FBR with respect to certain liabilities, including liabilities under the Securities Act. At December 31, 2017, the Company sold an aggregate of 6,575,062 shares of its common stock under the at-the-market offering program at an average market price of $6.10 per share, resulting in aggregate gross proceeds of approximately $40.1 million. In April 2017, the Company filed another shelf registration statement on Form S-3, which included a base prospectus covering the offering, issuance and sale of up to a maximum aggregate offering of $100.0 million of the Company’s common stock, preferred stock, debt securities, warrants, purchase contracts and/or units. At December 31, 2017, no securities had been sold pursuant to this registration statement.

Common Stock Reserved for Issua

Common Stock Reserved for Issuance	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Common Stock Reserved for Issuance	11. Common Stock Reserved for Issuance The common stock reserved for future issuance at December 31, 2017 and 2016 was as follows: December 31, 2017 2016 Shares underlying outstanding stock options 8,592,747 6,127,291 Shares available for future stock option grants 969,783 2,168,391 Shares issuable upon settlement of restricted stock units outstanding 149,636 151,240 ESPP shares available for issuance 1,103,481 667,670 Warrant to purchase common stock 3,393,755 1,707,736 Total shares of common stock reserved 14,209,402 10,822,328

Convertible Preferred Stock

Convertible Preferred Stock	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Convertible Preferred Stock	12. Convertible Preferred Stock In January 2015, the Company issued an aggregate of 162,407 shares of Series C convertible preferred stock to a new investor at a price of $5.84 per share for a total gross consideration of $950 thousand. In February 2015, the Company issued 2,564,652 shares of Series C convertible preferred stock to another investor at a price of $5.84 per share for total gross consideration of $15.0 million. In July 2015, upon the closing of the Merger, all of ViewRay Technologies, Inc.’s 30,381,987 shares of outstanding convertible preferred stock were converted into the Company’s common stock at a 1:1 conversion rate. As a result, the Company had no convertible preferred stock issued and outstanding at December 31, 2017, 2016 and 2015.

Warrants

Warrants	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Warrants	13. Warrants Preferred Stock Warrants In connection with a 2013 debt financing (see Note 6), the Company issued a warrant to purchase 128,231 shares of Series C convertible preferred stock. These warrants have an exercise price of $5.84 per share, and are exercisable any time at the option of the holder until December 16, 2023. The convertible preferred stock warrant was recorded as a liability and is adjusted to fair value at each balance sheet date, with the change in fair value being recorded as a component of other expense, net in the consolidated statements of operations and comprehensive loss. For the year ended December 31, 2015, the Company recognized a gain of $45 thousand related to the change in fair value of the warrant in the accompanying consolidated statements of operations and comprehensive loss. Upon the consummation of the Merger in July 2015, the warrant to purchase Series C convertible preferred stock was converted into the warrant to purchase 128,231 shares of the Company’s common stock. As a result, the fair value of the preferred stock warrant liability of $93 thousand was reclassified into additional paid-in capital. The Company used the Black-Scholes option-pricing model to estimate the fair value of the convertible preferred stock warrant upon conversion with the following assumptions: Upon the Closing of the 2015 Common Stock Warrants: Expected term (in years) 5.0 Expected volatility (%) 31.8% Risk-free interest rate (%) 1.7% Expected dividend yield (%) 0% Equity Classified Common Stock Warrants In connection with the Merger and the Private Placement, in July and August 2015, the Company issued warrants, or 2015 Placement Warrants, that provide the warrant holder the right to purchase 198,760 shares of common stock at an exercise price of $5.00 per share. These warrants were issued to private placement agents as payment for services provided. The 2015 Placement Warrants are exercisable at any time at the option of the holder until the five-year anniversary of their date of issuance. The Company estimated the aggregate fair value of 2015 Placement Warrants on issuance date to be $316 thousand which was recorded in additional paid-in capital as an offering cost against the total proceeds from the Private Placement. The fair value of the placement warrants was measured at their grant dates using the Black-Scholes pricing model and the following weighted average assumptions: Upon Issuance Common Stock Warrants: Expected term (in years) 5.0 Expected volatility (%) 31.8% Risk-free interest rate (%) 1.6% Expected dividend yield (%) 0% At December 31, 2017 and 2016, all of these equity classified warrants had not been exercised and remain outstanding. Liability Classified Common Stock Warrants In connection with the 2016 Private Placement, in August and September 2016, the Company issued warrants, the 2016 Placement Warrants, that provide the warrant holder the right to purchase 1,380,745 shares of common stock at an exercise price of $2.95 per share. These 2016 Placement Warrants are exercisable at any time at the option of the holder until the seven-year anniversary of their date of issuance. The 2016 Placement Warrants also contain protection whereby the warrants will expire immediately prior to the consummation of a change of control, as defined in the agreement, and holders have the right to receive cash in the amount equal to the Black-Scholes value of warrants. The 2016 Placement Warrants were accounted for as a liability at the date of issuance and are adjusted to fair value at each balance sheet date, with the change in fair value recorded as a component of other expense, net in the consolidated statements of operations and comprehensive loss. As separate classes of securities were issued in a bundled transaction, the gross proceeds from the 2016 Private Placement of $13.8 million was allocated first to the 2016 Placement Warrants based on their fair value upon issuance, and the residual was allocated to the common stock. The fair value upon issuance of $2.7 million for the 2016 Placement Warrants was estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions: expected term of seven years, expected volatility of 61.6%, risk-free interest rate of 1.4% and expected dividend yield of 0%. During the year ended December 31, 2017 and 2016, the Company recorded loss of $7.4 million and a gain of $3 thousand, respectively, related to the change in fair value of the 2016 Placement Warrants. The fair value of the 2016 Placement Warrants of $9.9 million and $2.7 million at December 31, 2017 and 2016, respectively, was estimated using the Black-Scholes option pricing model and the following weighted-average assumptions: December 31, 2017 2016 2016 Placement Warrants: Expected term (in years) 5.7 6.7 Expected volatility (%) 62.1% 63.6% Risk-free interest rate (%) 2.2% 2.3% Expected dividend yield (%) 0% 0% In connection with the January 2017 Private Placement, the Company issued warrants, the 2017 Placement Warrants, that provide the warrant holder the right to purchase 1,720,512 shares of common stock at an exercise price of $3.17 per share. These 2017 Placement Warrants became exercisable in July 2017 and expire in January 2024. As separate classes of securities were issued in a bundled transaction, the gross proceeds from the January 2017 Private Placement of $26.1 million was allocated first to the 2017 Placement Warrants based on its fair value upon issuance, and the residual was allocated to the common stock. The fair value upon issuance of $3.4 million for the 2017 Placement Warrants was estimated using the Black-Scholes option-pricing model with the following weighted-average assumptions: expected term of seven years, expected volatility of 62.9%, risk-free interest rate of 2.2% and expected dividend yield of 0%. During the year ended December 31, 2017, the Company recorded a loss of $9.2 million related to the change in fair value of the 2017 Placement Warrants. The fair value of the 2017 Placement Warrants of $12.5 million at December 31, 2017 was estimated using the Black-Scholes option pricing model and the following weighted-average assumptions: December 31, 2017 2017 Placement Warrants: Expected term (in years) 6.1 Expected volatility (%) 62.3% Risk-free interest rate (%) 2.3% Expected dividend yield (%) 0% In December 2017, 25,104 shares of 2016 Placement Warrant and 9,389 shares of 2017 Placement Warrant were exercised and the related warrant liability of $274 thousand was reclassified into additional paid-in capital upon exercise. At December 31, 2017, 1,355,641 shares of the 2016 Placement Warrant and 1,711,123 shares of the 2017 Placement Warrant were outstanding.

Stock-Based Compensation

Stock-Based Compensation	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	14. Stock-Based Compensation The Company adopted 2008 Stock Option and Incentive Plan, or 2008 Plan, and 2015 Equity Incentive Award Plan, or 2015 Plan, to its employees, officers, directors, advisors and consultants. With the establishment of the 2015 Plan, the Company no longer grants stock options under the 2008 Plan, and the shares available for future grants under the 2008 Plan were transferred to the 2015 Plan. Only stock options were granted under the 2008 Plan. The 2015 Plan provides for the grant of stock and stock-based awards including stock options, restricted stock awards, restricted stock units and stock appreciation rights. Options granted may be either incentive stock options or non-statutory stock options. Under the 2008 Plan, incentive stock options could only have been granted to employees with exercise prices of no less than the fair value of the common stock on the grant date and non-statutory options may be granted to employees or consultants at exercise prices of no less than 85% of the fair value of the common stock on the grant date, as determined by the board of directors. Under the 2015 Plan, for both inventive stock options and nonstatutory options, the exercise price should not be less than the fair value of the common stock on the date of grant. Under both the 2008 Plan and the 2015 Plan, if, at the time of grant, the optionee owns stock representing more than 10% of the voting power of all classes of stock of the Company, a 10% shareholder, the exercise price must be at least 110% of the fair value of the common stock on the grant date as determined by the board of directors. Options become exercisable generally ratably over four years, and expire in 10 years from the date of grant, or five years from the date of grant for 10% shareholders. In July 2015, the Company adopted the 2015 Employee Stock Purchase Plan, or 2015 ESPP, and 667,670 shares were reserved for issuance under the 2015 ESPP. At December 31, 2017 and 2016, no shares have been issued under the 2015 ESPP. A summary of the Company’s stock option activity and related information is as follows: Options Outstanding Shares Available for Grant Number of Stock Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual (Years) Aggregate Intrinsic Value (In Balance at December 31, 2016 2,168,391 6,127,291 2.60 7.3 7,800 Additional authorized 1,743,247 Granted (2,986,244 ) 2,986,244 5.65 Exercised — (420,377 ) 1.58 Cancelled 100,411 (100,411 ) 3.95 RSUs granted (56,022 ) — Balance at December 31, 2017 969,783 8,592,747 $ 3.69 7.4 $ 47,864 Vested and exercisable at December 31, 2017 5,011,207 $ 2.65 6.5 $ 33,130 Vested and expected to vest at December 31, 2017 8,303,413 $ 3.64 7.4 $ 46,655 The weighted-average grant date fair value of options granted to employees was $3.38, $2.72 and $3.13 per share for the year ended December 31, 2017, 2016 and 2015. The grant date fair value of options vested was $4.8 million, $2.4 million and $782 thousand, respectively, during the year ended December 31, 2017, 2016 and 2015. Aggregate intrinsic value represents the difference between the estimated fair value of the underlying common stock and the exercise price of outstanding, in-the-money options. The aggregate intrinsic value of options exercised was $2.6 million and $2.3 million for the year ended December 31, 2017 and 2016. The aggregate intrinsic value of options exercised was insignificant for the year ended December 31, 2015. At December 31, 2017, total unrecognized compensation cost related to stock-based awards granted to employees, net of estimated forfeitures, was $9.9 million which is expected to be recognized over a weighted-average period of 2.7 years. Determination of Fair Value The determination of the fair value of stock options on the date of grant using an option-pricing model is affected by the estimated fair value of the Company’s common stock, as well as assumptions regarding a number of complex and subjective variables. The variables used to calculate the fair value of stock options using the Black-Scholes option-pricing model include actual and projected employee stock option exercise behaviors, expected price volatility of the Company’s common stock, the risk-free interest rate and expected dividends. Each of these inputs is subjective and generally requires significant judgment to determine. Fair Value of Common Stock Prior to the Merger, the fair value of the common stock underlying the stock-based awards was determined by ViewRay Technologies, Inc.’s board of directors, with input from management and third-party valuations. Post-Merger and up through March 30, 2016, the Company’s common stock shares were listed on the OTC Bulletin Board. Beginning March 31, 2016, the Company’s common stock shares were listed on The NASDAQ Global Market, or NASDAQ. Fair value of the common stock is the adjusted closing price of the Company’s common stock on the trading date on these stock exchanges. Expected Term The expected term represents the period that the Company’s option awards are expected to be outstanding. The Company considers several factors in estimating the expected term of options granted, including the expected lives used by a peer group of companies within the Company’s industry that the Company considers to be comparable to its business and the historical option exercise behavior of its employees, which the Company believes is representative of future behavior. Expected Volatility As the Company does not have a sufficient trading history for its common stock, the expected stock price volatility for the Company’s common stock was estimated by taking the average historic price volatility for industry peers based on daily price observations over a period equivalent to the expected term of the stock option grants. Industry peers consist of several public companies in the Company’s industry which were the same as the comparable companies used in the common stock valuation analysis. The Company intends to continue to consistently apply this process using the same or similar public companies until a sufficient amount of historical information regarding the volatility of its own share price becomes available, or unless circumstances change such that the identified companies are no longer similar to the Company, in which case, more suitable companies whose share prices are publicly available would be used in the calculation. Risk-Free Interest Rate The risk-free interest rate is based on the zero-coupon U.S. Treasury notes, with maturities similar to the expected term of the options. Expected Dividend Yield The Company does not anticipate paying any dividends in the foreseeable future and, therefore, uses an expected dividend yield of zero in the Black-Scholes option-valuation model. In addition to the Black-Scholes assumptions discussed immediately above, the estimated forfeiture rate also has a significant impact on the related stock-based compensation. The forfeiture rate of stock options is estimated at the time of grant and revised in subsequent periods if actual forfeitures differ from those estimates. The Company uses historical data to estimate pre-vesting option forfeitures and records stock-based compensation expense only for those awards that are expected to vest. The fair value of employee stock options was estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted-average assumptions: Year Ended December 31, 2017 2016 2015 Expected term (in years) 5.9 6.0 5.9 Expected volatility (%) 66.0% 67.1% 68.7% Risk-free interest rate (%) 2.1% 1.3% 1.8% Expected dividend yield (%) 0.0% 0.0% 0.0% Restricted Stock Units From time to time, the Company grants Restricted Stock Units, or RSUs, to its board of directors for their services. These RSUs were fully vested upon issuance and will be released and settled upon termination of the board services or the occurrence of a change in control event. In September 2016 and November 2017, the Company granted 112,578 shares and 43,554 shares of RSUs to its board members, respectively, and 18,964 shares of these RSUs were released in December 2017 upon termination of one board member. In December 2016, the Company granted 18,017 shares of RSUs to certain executive officers for bonus and 20,645 shares of RSUs to a consultant for service. These RSUs were fully vested upon issuance and released in fiscal year 2017. In November 2017, the Company granted 12,468 shares of RSUs to one executive officer upon his termination. These RSUs were fully vested upon issuance but not released in fiscal year 2017, although the conditions to release these RSUs were satisfied at December 31, 2017. The fair value of RSUs is based on the closing market price of the Company’s common stock on the grant date. The weighted-average grant date fair value of RSUs granted in fiscal year 2016 and 2017 was $3.52 per share and $8.02 per share, respectively, and the Company recorded stock based compensation expense related to RSUs of $532 thousand and $449 thousand during the year ended December 31, 2016 and 2017, which was included in general and administrative expenses in the accompanying statements of operations and comprehensive loss. There was no stock based compensation expense related to RSUs during the year ended December 31, 2015. Stock-Based Compensation Expense Total stock-based compensation expense recognized in the Company’s consolidated statements of operations and comprehensive loss is classified as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development $ 952 $ 593 $ 262 Selling and marketing 303 120 50 General and administrative 4,064 2,194 754 Total stock-based compensation expense $ 5,319 $ 2,907 $ 1,066 During the years ended December 31, 2017, 2016 and 2015 there were no stock-based compensation expenses capitalized as a component of inventory or recognized in cost of revenue. Stock-based compensation relating to stock-based awards granted to consultants was insignificant for the years ended December 31, 2017, 2016 and 2015.

Income Taxes

Income Taxes	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Income Taxes	15. Income Taxes On December 22, 2017, the Tax Cuts and Jobs Act (the “2017 Tax Act”) was enacted. The 2017 Tax Act includes a number of changes to existing U.S. tax laws that impact the Company, most notably a reduction of the top U.S. corporate income tax rate from 35 percent to 21 percent for tax years beginning after December 31, 2017. The Company recognized the income tax effects of the 2017 Tax Act in its 2017 financial statements in accordance with SEC Staff Accounting Bulletin No. 118 (“SAB 118”), which provides guidance for the application of ASC Topic 740, Income Taxes, in the reporting period in which the 2017 Tax Act was signed into law. As such, the Company’s financial results reflect the income tax effects of the 2017 Tax Act for which the accounting under ASC Topic 740 is complete and provisional amounts for those specific income tax effects of the 2017 Tax Act for which the accounting under ASC Topic 740 is incomplete but a reasonable estimate could be determined. Upon completion of our 2017 U.S. income tax return in 2018 we may identify additional remeasurement adjustments to our recorded deferred tax assets. We will continue to assess our provision for income taxes as future guidance is issued, but do not currently anticipate significant revisions will be necessary. Any such revisions will be treated in accordance with the measurement period guidance outlined in SAB 118. The changes to existing U.S. tax laws as a result of the 2017 Tax Act, which we believe have the most significant impact on the Company’s federal income taxes are as follows: Reduction of the U.S. Corporate Income Tax Rate The Company measures deferred tax assets and liabilities using enacted tax rates that will apply in the years in which the temporary differences are expected to be recovered or paid. Accordingly, the Company’s deferred tax assets and liabilities were remeasured to reflect the reduction in the U.S. corporate income tax rate from 35 percent to 21 percent. This resulted in a $38.7 million decrease in net deferred tax assets and a corresponding $38.7 million decrease to the valuation allowance as of December 31, 2017. Income Tax Expense The following reconciles the differences between income taxes computed at the federal income tax rate and the provision for income taxes: Year Ended December 31, 2017 2016 2015 Expected income tax benefit at the federal statutory rate 34.0 % 34.0 % 34.0 % State taxes, net of federal benefit 0.0 0.0 (0.8 ) Change in effective tax rate (54.1 ) 0.0 (0.9 ) Non-deductible items and other 0.5 (0.7 ) (0.5 ) Federal and state credits 0.5 0.6 (0.7 ) Change in valuation allowance 19.1 (33.9 ) (31.1 ) Total 0.0 % 0.0 % 0.0 % Deferred income taxes reflect the net effects of temporary differences between the carrying amounts of assets and liabilities for financial reporting purposes and the amounts used for income tax purposes. The principal components of the Company’s net deferred tax assets consisted of the following at December 31, 2017 and 2016 (in thousands): Year Ended December 31, 2017 2016 Net operating loss carryforwards $ 61,049 $ 75,036 Research and development tax credits 3,731 2,131 Reserves and accruals 1,168 1,791 Other 6,611 4,594 Total deferred tax assets 72,559 83,552 Valuation allowance (72,559 ) (83,552 ) Net deferred tax assets $ — $ — The Company maintains a valuation allowance related to its deferred tax asset position when management believes it is more likely than not that the net deferred tax assets will not be realized in the future. The Company’s valuation allowance decreased by $11.0 million and increased by $17.4 million during the year ended December 31, 2017 and 2016. At December 31, 2017, the Company had federal net operating loss carryforwards of $266.3 million, which begin to expire in the year ending December 31, 2024, and $144.8 million related to state net operating loss carryforwards, which begin to expire in the year ending December 31, 2019. The Company had federal research and development tax credit carryforwards of $3.8 million, and state carryforwards of $1.3 million at the year ended December 31, 2017. These credits begin to expire in the year ending December 31, 2024. Under the provisions of the Internal Revenue Code, or IRC, net operating loss and credit carryforwards and other tax attributes may be subject to limitation if there has been a significant change in ownership of the Company, as defined by the IRC. The Company believes it has experienced at least one ownership change in the past. The Company is currently analyzing the tax impact of such ownership change on its federal net operating loss and credit carryforwards. Future change in the Company’s ownership could result in limitations on net operating loss and credit carryforwards. Because of the net operating loss and credit carryforwards, all of the Company’s federal tax returns and state returns since the year ended December 31, 2004 remain subject to federal and California examination. The Company accounts for uncertain tax positions using a “more-likely-than-not” threshold. The evaluation of uncertain tax positions is based on factors including, but not limited to, changes in tax law, the measurement of tax positions taken or expected to be taken in tax returns, the effective settlement of matters subject to audit, new audit activity and changes in facts or circumstances related to a tax position. The Company evaluates these tax positions on an annual basis. In addition, the Company also accrues for potential interest and penalties related to unrecognized tax benefits in income tax expense. At December 31, 2017 and 2016, the Company’s unrecognized tax benefits consist of the following: Year Ended December 31, 2017 2016 Unrecognized tax benefit, beginning of period $ 940 $ 742 Gross increases — current year tax positions 327 198 Gross increases — prior year tax positions 73 — Gross decreases — prior year tax positions (205 ) — Unrecognized tax benefit, end of period $ 1,135 $ 940

Employee Benefits

Employee Benefits	12 Months Ended
	Dec. 31, 2017
Postemployment Benefits [Abstract]
Employee Benefits	16. Employee Benefits The Company has a 401(k) Plan which covers its eligible employees. The 401(k) Plan permits the participants to defer a portion of their compensation in accordance with the provisions of Section 401(k) of the IRC. At its discretion, the Company can match a portion of the participants’ contributions or make profit-sharing contributions. There was no matching or profit-sharing contributions during the years ended December 31, 2017, 2016 or 2015.

Net Loss per Share

Net Loss per Share	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Net Loss per Share	17. Net Loss per Share The following table sets forth the computation of the Company’s basic and diluted net loss per share for the periods presented (in thousands, except share and per share data): Year Ended December 31, 2017 2016 2015 Net loss $ (72,176 ) $ (50,636 ) $ (44,995 ) Weighted-average common shares used in computing net loss per share, basic and diluted 58,457,868 40,068,307 17,432,434 Net loss per share, basic and diluted $ (1.23 ) $ (1.26 ) $ (2.58 ) The following weighted-average common stock equivalents were excluded from the calculation of diluted net loss per share for the periods presented because including them would have had an anti-dilutive effect: Year Ended December 31, 2017 2016 2015 Convertible preferred stock (if converted) — — 16,558,330 Options to purchase common stock 7,914,067 6,181,015 5,032,768 Convertible preferred stock warrant — — 71,318 Common stock warrant 3,345,674 804,248 142,513 Restricted stock units 108,107 33,835 —

Segment and Geographic Informat

Segment and Geographic Information	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Segment and Geographic Information	18. Segment and Geographic Information The Company has one business activity, which is radiation therapy technology combined with magnetic resonance imaging, and operates in one reportable segment. The Company’s chief operating decision-maker, its chief executive officer, reviews its operating results on an aggregate basis for purposes of allocating resources and evaluating financial performance. Also, the Company does not have segment managers as the Company manages its operations as a single operating segment. The following table sets forth revenue by geographic area on the customers’ location (in thousands): Year Ended December 31, 2017 2016 2015 United States $ 11,506 $ 1,106 $ 5,332 UAE 5,675 — — Korea 5,504 182 4,988 Israel 5,309 — — China 4,680 — — Japan 753 10,375 — Netherlands 317 5,486 — Italy 298 5,088 — Rest of world — — 70 Total revenue $ 34,042 $ 22,237 $ 10,390 At December 31, 2017 and 2016, all long-lived assets are located in the United States.

Related Party Transactions

Related Party Transactions	12 Months Ended
	Dec. 31, 2017
Related Party Transactions [Abstract]
Related Party Transactions	19. Related Party Transactions As discussed in Note 8, the Company pays a royalty to UFRF, a common stockholder, related to a licensing agreement. In January 2017, the Company entered into a sales consulting agreement with Puissance Capital Management, or PCM, to assist with business development activities in a key market in Asia. PCM is the investment manager of Puissance Cross Board Opportunities LLP, a stockholder in the Company. Theodore T. Wang, Ph.D., a member of the Company’s board of directors, is the managing member of the general partners of PCM. The sales consulting agreement has a term of one year with a total consideration of $1.3 million.

Subsequent Events

Subsequent Events	12 Months Ended
	Dec. 31, 2017
Subsequent Events [Abstract]
Subsequent Events	20. Subsequent Event In February 2018, the Company entered into a Securities Purchase Agreement pursuant to which it sold 4.1 million shares of common stock, 3.0 million shares of Series A convertible preferred stock and warrants to purchase 1.4 million shares of common stock for total gross proceeds of $59.1 million. These w arrants have an exercise price of , became exercisable upon issuance at the closing and expire seven years from the date of issuance.

Summary of Significant Accoun28

Summary of Significant Accounting Policies (Policies)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States, or GAAP, and pursuant to the rules and regulation of the Securities and Exchanges Commission, or SEC. The consolidated financial statements include the accounts of ViewRay, Inc. and its wholly-owned subsidiary, ViewRay Technologies, Inc. All inter-company accounts and transactions have been eliminated in consolidation.
Use of Estimates	Use of Estimates The preparation of the consolidated financial statements in conformity with GAAP requires management to make estimates and assumptions that affect the amounts reported and disclosed in the consolidated financial statements and accompanying notes. Such estimates include, but are not limited to, allocation of revenue to its multiple deliverable elements, inventory write-downs to reflect net realizable value, assumptions used in the valuation of stock-based awards and warrant liability, and valuation allowances against deferred tax assets. Actual results could differ from those estimates.
Cash and Cash Equivalents	Cash and Cash Equivalents The Company considers all highly liquid investments purchased with an original maturity of three months or less to be cash equivalents. The Company deposits its cash primarily in checking and money market accounts.
Restricted Cash	Restricted Cash At December 31, 2017 and 2016, the Company had an aggregate of $0.9 million of outstanding letters of credit related to its operating leases and its contractual obligations with distributors and customers. The letters of credit are collateralized by a restricted cash deposit account, which is presented as part of noncurrent assets on the balance sheets because the Company is not certain when the restriction will be lifted on the collateralized letters of credit. At December 31, 2017, and 2016, no amounts were drawn on the letters of credit. The restricted cash balance as of December 31, 2017 also includes $0.2 million collateral for a credit card account.
Concentration of Credit Risk, Other Risks and Uncertainties	Concentration of Credit Risk, Other Risks and Uncertainties Financial instruments that potentially subject the Company to concentrations of credit risk consist primarily of cash and cash equivalents and accounts receivable. Cash and cash equivalents are deposited in checking and money market accounts with various financial institutions. At times, cash balances may be in excess of the amounts insured by the Federal Deposit Insurance Corporation. Management believes the financial risk associated with these balances is minimal and has not experienced any losses to date. The Company performs periodic credit evaluations of its customers’ financial condition and generally requires deposits from its customers. The Company’s accounts receivable was derived from billings to customers. The Company’s customers representing greater than 10% of accounts receivable and revenue for the periods presented were as follows: Revenue Accounts Receivables Year Ended December 31, December 31, Customers 2017 2016 2015 2017 2016 Customer A 17% Customer B 17% Customer C 16% 48% Customer D 16% 24% Customer E 14% 16% Customer F 10% Customer G 36% Customer H 47% 49% Customer I 25% Customer J 23% 41% Customer K 43% The Company’s future results of operations involve a number of risks and uncertainties. Factors that could affect the Company’s future operating results and cause actual results to vary materially from expectations include, but are not limited to, rapid technological change, continued acceptance of MRIdian, competition from substitute products and larger companies, protection of proprietary technology, ability to maintain distributor relationships and dependence on key individuals. Furthermore, new products to be developed by the Company require approval from the FDA or other international regulatory agencies prior to commercial sales. There can be no assurance that the Company’s future products will receive the necessary clearances. The Company relies on a concentrated number of suppliers to manufacture essentially all of the components used in MRIdian. The Company’s suppliers may encounter problems during manufacturing due to a variety of reasons, including failure to comply with applicable regulations, including the FDA’s Quality System Regulation, equipment malfunction and environmental factors, any of which could delay or impede our ability to meet demand.
Accounts Receivables and Allowance for Doubtful Accounts	Accounts Receivables and Allowance for Doubtful Accounts Accounts receivable are recorded at the invoiced amount, net of any allowance for doubtful accounts, and do not bear interest. The allowance for doubtful accounts, if any, is based on the assessment of the collectability of customer accounts. Based on the specific customers and the current economic conditions, there was no allowance for doubtful accounts recorded at December 31, 2017 and 2016.
Fair Value of Financial Instruments	Fair Value of Financial Instruments Financial instruments consist of cash and cash equivalents, accounts receivable, restricted cash, prepaid expenses and other current assets, accounts payable, accrued liabilities, warrant liability and long-term debt. Cash equivalents are stated at amortized cost, which approximates fair value at the balance sheet dates, due to the short period of time to maturity. Accounts receivable, prepaid expenses and other current assets, accounts payable and accrued liabilities are stated at their carrying value, which approximates fair value due to the short time to the expected receipt or payment date. The warrant liability is carried at fair value. The carrying amount of the Company’s long-term debt approximates fair value as the stated interest rate approximates market rates currently available to the Company.
Inventory and Deposits on Purchased Inventory	Inventory and Deposits on Purchased Inventory Inventory consists of purchased components for assembling MRIdian systems and other direct and indirect costs associated with MRIdian system installation. Inventory is stated at the lower of cost (on a weighted average cost basis) or market value. All inventories expected to be placed in service during the normal operating cycle of the Company for the delivery and assembly of MRIdian systems, including items expected to be on hand for more than one year, are classified as current assets. The Company reduces the carrying value of its inventory for the difference between cost and net realizable value and records a charge to cost of product revenues for the amount required to reduce the carrying value of inventory to net realizable value. The Company recorded an inventory lower of cost and market adjustment of $0.9 million, $1.9 million and $2.6 million during the years ended December 31, 2017, 2016 and 2015, respectively. The Company records inventory items which have been paid for but not yet received and title has not yet transferred to the Company as deposits on purchased inventory. Deposits on purchased inventory are included within current assets as the related inventory items are expected to be received and used in MRIdian systems within the Company’s normal operating cycle. The Company assesses the recoverability of deposits on purchased inventory based on credit assessments of the vendors and their history supplying these assets. At December 31, 2017, the Company did not have any instances whereby deposits for purchased inventory were written off or the purchased inventory was not delivered.
Shipping and Handling Costs	Shipping and Handling Costs Shipping and handling costs for product shipments to customers are included in cost of product revenue. Shipping and handling costs incurred for inventory purchases are capitalized in inventory and expensed in cost of product revenue. These costs are not passed on to customers.
Property and Equipment	Property and Equipment Property and equipment are recorded at cost. Depreciation is computed over estimated useful lives, ranging from two to 15 years, of the related assets using the straight-line method. Acquired software is recorded at cost. Amortization of acquired software generally occurs over three years using the straight-line method. Leasehold improvements are amortized on a straight-line basis over the shorter of the useful life or term of the lease. Demonstration units, which are the Company products used for demonstration purpose for customers and/or potential customers, and generally not intended to be sold, are amortized by the straight-line method. Upon retirement or sale, the cost and related accumulated depreciation are removed from the balance sheet and the resulting gain or loss is recorded to general and administrative expense in the accompanying statements of operations and comprehensive loss. Routine expenditures for maintenance and repairs are expensed as incurred. Depreciation and amortization periods for property and equipment are as follows: Property and Equipment Estimated Useful Life Prototype 2 – 10 years Machinery and equipment 5 – 15 years Furniture and fixture 5 – 10 years Software 3 years Leasehold improvements Lesser of estimated useful life or remaining lease term
Asset Retirement Obligation	Asset Retirement Obligation In connection with certain lease agreements entered into in October 2015, the Company has a legal requirement to remove long-lived assets constructed on leased property and to restore the leased property to its original condition. The Company records the fair value of the liability for a legal obligation to retire an asset in the period in which the obligation is incurred if a reasonable estimate of fair value can be made. The Company measures the fair value of the asset retirement obligation based upon the present value of the expected future payments, and recognized asset retirement obligation of $250,000 at inception. The liability is accreted to its present value each period and the capitalized cost is depreciated over the remaining lease term. Accretion expense is calculated by applying the effective interest rate to the carrying amount of the liability at the beginning of each period. The effective interest rate is the credit-adjusted risk-free rate applied when the liability was initially measured and recognized. At December 31, 2017, the Company had outstanding asset retirement obligations of $334,000, which was included in other long-term liabilities in the accompanying consolidated balance sheets. For the years ended December 31, 2017, 2016 and 2015, the Company recognized accretion expenses of $40,000, $36,000 and $8,000 in the accompanying statements of operations and comprehensive loss.
Intangible Assets	Intangible Assets Intangible assets consist primarily of patents and license acquisition costs associated with certain technology components incorporated into the Company’s MRIdian systems. The Company capitalizes the cost and amortizes it on a straight-line basis over the estimated useful lives, which is generally three years for license cost and five to seven years for patents.
Impairment of Long-Lived Assets	Impairment of Long-Lived Assets The Company reviews the recoverability of long-lived assets, including equipment, leasehold improvements, software and intangible assets when events or changes in circumstances occur that indicate that the carrying value of the asset may not be recoverable. The assessment of possible impairment is based on the ability to recover the carrying value of the assets from the expected future cash flows (undiscounted and without interest charge) of the related operations. If these cash flows are less than the carrying value of such assets, an impairment loss for the difference between the estimated fair value and carrying value is recorded. There was no impairment loss recognized during the years ended December 31, 2017, 2016 and 2015.
Deferred Offering Costs	Deferred Offering Costs ViewRay Technologies, Inc. capitalized qualified legal, accounting and other direct costs related to its efforts to raise capital through a public sale of its common stock in its planned IPO. These costs were recorded in deferred offering costs in the accompanying balance sheets
Comprehensive Loss	Comprehensive Loss Comprehensive loss is the change in equity of a company during a period from transactions and other events and circumstances, excluding transactions resulting from investment owners and distribution to owners. For the periods presented, comprehensive loss did not differ from net loss.
Revenue Recognition	Revenue Recognition The Company derives revenue primarily from the sale of the systems and related services, which are sales of MRIdian, as well as support and maintenance services on sold systems. In all sales arrangements, the Company recognizes revenues when there is persuasive evidence of an arrangement, the fee is fixed or determinable, collection of the fee is reasonably assured and delivery has occurred. For sales of MRIdian systems that the Company is required to install at the customer site, product revenue is recognized upon receipt of customer acceptance. For sales of MRIdian systems that the Company is not responsible for installation, product revenue is recognized when the entire system is delivered and title and risk of loss are transferred to the customer. For sales of the related support and maintenance services, the Company recognizes service revenue on a straight-line basis over the service contract term, which is typically 12 months.
Multiple Elements	Multiple Elements Based on the nature of the Company’s business, it frequently enters into sales arrangements with customers that contain multiple elements or deliverables. The principal deliverables consist of (i) sale of MRIdian systems, which generally includes installation, site preparation and software, and (ii) product support, which includes extended service and maintenance. The Company determines selling prices of each deliverable using vendor specific objective evidence, or VSOE, if it exists, or third-party evidence, or TPE. If neither VSOE nor TPE exists for a deliverable, the Company uses best estimated selling price, or BESP. The Company allocates revenue to each standalone deliverable using the relative fair values for each deliverable as determined by BESP. The Company regularly reviews VSOE, TPE and BESP for all of its MRIdian systems and services.
Product Revenue	Product Revenue Product revenue is derived primarily from the sales of MRIdian. The system contains both software and non-software components that together deliver essential functionality. However, because MRIdian includes hardware products as well as software components that function together with the hardware components to deliver MRIdian’s essential functionality, the revenue from the sale of MRIdian systems does not fall within the scope of the software revenue recognition rules. The Company’s customer contracts generally call for on-site assembly of the system components and system integration. Once the system installation is completed, the Company performs a detailed demonstration with the customer showing that MRIdian meets the standard product specifications. After successful demonstration, the customer signs a document indicating customer’s acceptance. For sales of MRIdian systems that the Company is required to install at the customer site, revenue recognition occurs when the customer acknowledges that the system operates in accordance with standard product specifications, the customer accepts the installed unit and title and risk of loss are transferred to the customer. Certain customer contracts with distributors do not require installation at the customer site, and the distributors typically have its own or engage a qualifying third-party certified technician to perform the installation. For sales of MRIdian systems when the Company is not responsible for installation, revenue recognition occurs when the entire system is delivered and title and risk of loss are transferred to the customer. All contracts include customer deposits upon signing of the agreement with final payment generally due upon customer acceptance.
Service Revenue	Service Revenue Service revenue is derived primarily from maintenance services. Service revenue is recognized ratably over the service period.
Distribution Rights Revenue	Distribution Rights Revenue The Company entered into a distribution agreement with Itochu Corporation pursuant to which it appointed Itochu as its exclusive distributor for the promotion, sale and delivery of MRIdian products within Japan. In consideration of the exclusive distribution rights granted, the Company received $4.0 million which was recorded as deferred revenue and starting in August 2016 was recognized as distribution rights revenue on a straight-line basis over the remaining term of the distribution agreement of approximately 8.5 years .
Customer Deposits	Customer Deposits Customer deposits represent payments received in advance of system installation. For domestic sales, advance payments received prior to inventory shipments and customer acceptance are recorded as customer deposits. For international sales, advance payments are initially recorded as customer deposits and are subsequently reclassified to deferred revenue upon inventory shipment when the title and risk of loss of inventory items transfer to customers. All customer deposits, including those that are expected to be a deposit for more than one year, are classified as current liabilities based on consideration of the Company’s normal operating cycle (the time between acquisition of the inventory components and the final cash collection from customers on these inventory components) which is in excess of one year.
Deferred Revenue and Deferred Cost of Revenue	Deferred Revenue and Deferred Cost of Revenue Deferred revenue consists of deferred product revenue and deferred service revenue. Deferred product revenue arises from timing differences between the fulfillment of other contract deliverables and satisfaction of all revenue recognition criteria consistent with the Company’s revenue recognition policy. Deferred service revenue results from the advance billing for services to be delivered over a period of time. Deferred revenues expected to be realized within one year are classified as current liabilities. Deferred cost of revenue consists of cost for inventory items that have been shipped with title and risk of loss transferred to the customer but the customer acceptance has not been received. Deferred cost of revenue is included as part of current assets as the corresponding deferred product revenue is expected to be realized within one year. The inventories recorded in deferred cost of revenue are also included in the inventory lower of cost or market analysis. At December 31, 2017 and 2016, no reserve was required for deferred cost of revenue.
Research and Development Costs	Research and Development Costs Expenditures, including payroll, contractor expenses and supplies, for research and development of products and manufacturing processes are expensed as incurred. Software development costs incurred subsequent to establishing technological feasibility are capitalized through the general release of MRIdian systems that contain the embedded software elements. Technological feasibility is demonstrated by the completion of a working model. The Company has not capitalized any software development costs at December 31, 2017 or 2016, since the costs incurred subsequent to achieving technological feasibility and completing the research and development for the software components were immaterial.
Stock-Based Compensation	Stock-Based Compensation The Company uses the Black-Scholes option-pricing model as the method for estimating the fair value of stock options. The Black-Scholes option-pricing model requires the use of highly subjective and complex assumptions that determine the fair value of share-based awards, including the options’ expected term and the price volatility of the underlying stock
Medical Device Excise Tax	Medical Device Excise Tax Medical Device Excise Tax, or MDET, Section 4191 of the Internal Revenue Code enacted by the Health Care and Education Reconciliation Act of 2010, in conjunction with the Patient Protection and Affordable Care Act, established a 2.3% excise tax on medical devices sold domestically which, due to subsequent legislative amendments, was suspended from January 1, 2016 to December 31, 2017. MDET was suspended for another two years after the stopgap bill was signed by the President in January 2018 The Company included MDET in cost of product revenue during the year ended December 31, 2015, net of amounts directly billed to the customer for this tax, if any.
Deferred Commissions	Deferred Commissions Deferred commissions are the direct and incremental costs directly associated with the MRIdian system contracts with customers, which primarily consist of sales commissions to our direct sales force. The commissions are deferred and expensed in proportion to the revenue recognized upon the acceptance of the MRIdian system. At December 31, 2017 and 2016, the Company had $3.5 million and $2.6 million deferred commissions recorded as part of prepaid expenses and other current assets on the accompanying consolidated balance sheets.
Income Taxes	Income Taxes The Company uses the asset and liability method of accounting for income taxes. Deferred tax assets and liabilities are recognized for the estimated future tax consequences attributable to differences between the financial statement carrying amounts of existing assets and liabilities and their respective tax bases. Deferred tax assets and liabilities are measured using enacted tax rates expected to apply to taxable income in the years in which those temporary differences are expected to be recovered or settled. Deferred tax expense or benefit is the result of changes in the deferred tax assets and liabilities. Valuation allowances are established when necessary to reduce deferred tax assets where, based upon the available evidence, management concludes that it is more-likely-than not that the deferred tax assets will not be realized. Because of the uncertainty of the realization of the deferred tax assets, the Company has recorded a full valuation allowance against its net deferred tax assets. In evaluating the ability to recover its deferred income tax assets, the Company considers all available positive and negative evidence, including its operating results, ongoing tax planning and forecasts of future taxable income on a jurisdiction-by-jurisdiction basis. In the event the Company was to determine that it would be able to realize its deferred income tax assets in the future in excess of their net recorded amount, it would make an adjustment to the valuation allowance which would reduce the provision for income taxes. Reserves are provided for tax benefits for which realization is uncertain. Such benefits are only recognized when the underlying tax position is considered more likely than not to be sustained on examination by a taxing authority, assuming they possess full knowledge of the position and facts. It is the Company’s policy to include any penalties and interest related to income taxes in its income tax provision; however, the Company currently has no penalties or interest related to income taxes. The earliest year that the Company is subject to examination is the year ended December 31, 2004.
Warrant Liability	Warrant Liability Convertible Preferred Stock Warrant Liability The Company’s warrant to purchase convertible preferred stock was classified as a liability on the consolidated balance sheets at fair value upon issuance because the warrant is exercisable for contingently redeemable preferred stock which is classified outside of stockholders’ equity (deficit). The warrant was subject to re-measurement to fair value at each balance sheet date, and any change in fair value was recognized in the consolidated statements of operations and comprehensive loss as other expense, net. In July 2015, upon the Merger of the Company and ViewRay Technologies, Inc., and the Private Placement, the convertible preferred stock warrants were converted into warrants to purchase the Company’s common stock, and the fair value of the preferred stock warrant liability was reclassified to additional paid-in capital. Common Stock Warrant Liability Certain warrants to purchase common stock provide for cash settlement in the event of change in control, and are classified as liabilities on the balance sheets at fair value upon issuance (see Note 14). These warrants are subject to re-measurement to fair value at each balance sheet date, and any change in fair value are recognized in the consolidated statements of operations and comprehensive loss as other expense, net. Upon exercise or expiration of the warrants, the related warrant liability will be reclassified to additional paid-in capital.
Net Loss per Share	Net Loss per Share The Company’s basic net loss per share is calculated by dividing the net loss by the weighted-average number of shares of common stock outstanding for the period. Contingently issuable shares are included in the computation of basic net loss per share as of the date that all necessary conditions have been satisfied and issuance of the shares is no longer contingent. The diluted net loss per share is computed by giving effect to all potential common stock equivalents outstanding for the period determined using the treasury stock method. For purposes of this calculation, stock options, restricted stock units and warrants to purchase common stock are considered to be common stock equivalents but have been excluded from the calculation of diluted net loss per share as their effect is anti-dilutive.
Recent Accounting Pronouncements	Recent Accounting Pronouncements In May 2014, the Financial Accounting Standards Board (“FASB”) issued ASU No. 2014-09, Revenue from Contracts with Customers (Topic 606) The Company will adopt Topic 606 on January 1, 2018 using the full retrospective method which requires the Company to restate each prior reporting period presented. Based on the nature of its sales arrangements, the Company does not believe the adoption of the new standards will have a material impact on the amount or timing of its revenue recognition, and the Company’s product revenue, service revenue and distribution rights revenue will remain substantially unchanged. As a result, the adoption of the new standards will have no material impact on the Company’s prior period financial statements. The Company expects to update the related disclosures upon adoption of the new standards in In February 2016, the FASB issued ASU No. 2016-02, Leases (Topic 842) As disclosed in Note 7, future minimum payments under noncancelable operating leases are approximately $2.2 million. In August 2016, the FASB issued ASU No. 2016-15, Statement of Cash Flows (Topic 230): Classification of Certain Cash Receipts and Cash Payments, Statement of Cash Flows (Topic 230): Restricted Cash, In May 2017, the FASB issued ASU No. 2017-09, Compensation-Stock Compensation (Topic 718): Scope of Modification Accounting
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements In July 2015, the FASB issued ASU No. 2015-11, Simplifying the Measurement of Inventory In March 2016, the FASB issued ASU No. 2016-09, Compensation – Stock Compensation (Topic 718 ): Improvements to Employee Share-Based Payment Accounting

Summary of Significant Accoun29

Summary of Significant Accounting Policies (Tables)	12 Months Ended
	Dec. 31, 2017
Accounting Policies [Abstract]
Schedule of Customers Representing Greater than 10% of Accounts Receivable and Revenue	The Company’s customers representing greater than 10% of accounts receivable and revenue for the periods presented were as follows: Revenue Accounts Receivables Year Ended December 31, December 31, Customers 2017 2016 2015 2017 2016 Customer A 17% Customer B 17% Customer C 16% 48% Customer D 16% 24% Customer E 14% 16% Customer F 10% Customer G 36% Customer H 47% 49% Customer I 25% Customer J 23% 41% Customer K 43%
Schedule of Depreciation and Amortization Periods for Property and Equipment	Depreciation and amortization periods for property and equipment are as follows: Property and Equipment Estimated Useful Life Prototype 2 – 10 years Machinery and equipment 5 – 15 years Furniture and fixture 5 – 10 years Software 3 years Leasehold improvements Lesser of estimated useful life or remaining lease term

Balance Sheet Components (Table

Balance Sheet Components (Tables)	12 Months Ended
	Dec. 31, 2017
Organization Consolidation And Presentation Of Financial Statements [Abstract]
Schedule of Property and Equipment	Property and equipment consisted of the following (in thousands): December 31, 2017 2016 Prototype $ 11,929 $ 6,405 Machine and equipment 7,831 6,057 Leasehold improvements 4,438 4,371 Furniture and fixtures 558 368 Software 1,142 1,028 Construction in progress - 5,498 Property and equipment, gross 25,898 23,727 Less: accumulated depreciation and amortization (14,334 ) (12,167 ) Property and equipment, net $ 11,564 $ 11,560
Summary of Intangible Assets	Intangible assets consisted of the following (in thousands): December 31, 2017 2016 License cost $ 512 $ 512 Patents 104 104 Intangible assets, gross 616 616 Accumulated amortization (538 ) (519 ) Intangible assets, net $ 78 $ 97
Summary of Estimated Future Amortization Expense	At December 31, 2017, the estimated future amortization expense of purchased intangible assets was as follows (in thousands): Year Ended December 31, Estimated Amortization Expense 2018 $ 19 2019 19 2020 19 2021 10 2022 3 Thereafter 8 Total amortization expense $ 78
Schedule of Accrued Liabilities	Accrued liabilities consisted of the following (in thousands): December 31, 2017 2016 Accrued payroll and related benefits $ 3,944 $ 4,274 Accrued accounts payable 2,671 1,202 Tax payable 149 13 Accrued legal and accounting 322 509 Other 121 336 Total accrued liabilities $ 7,207 $ 6,334
Schedule of Deferred Revenue	Deferred revenue consisted of the following (in thousands): December 31, 2017 2016 Deferred revenue: Product $ 18,861 $ 5,050 Services 1,182 1,561 Distribution rights 3,346 3,822 Total deferred revenue 23,389 10,433 Less: current portion of deferred revenue (20,151 ) (6,515 ) Noncurrent portion of deferred revenue $ 3,238 $ 3,918

Fair Value of Financial Instr31

Fair Value of Financial Instruments (Tables)	12 Months Ended
	Dec. 31, 2017
Fair Value Disclosures [Abstract]
Schedule of Fair Value of Financial Liabilities	The following table sets forth the fair value of the Company’s financial liabilities by level within the fair value hierarchy (in thousands): At December 31, 2017 Level 1 Level 2 Level 3 Total 2017 Placement Warrants Liability $ — $ — $ 12,487 $ 12,487 2016 Placement Warrants Liability — — 9,933 9,933 Total Warrant Liability $ — $ — $ 22,420 $ 22,420 At December 31, 2016 Level 1 Level 2 Level 3 Total 2016 Placement Warrants Liability $ — $ — $ 2,723 $ 2,723
Summary of Changes in Fair Value of Level 3 Financial Liabilities	The following table sets forth a summary of the changes in the fair value of the Company’s Level 3 financial liabilities (in thousands): Year Ended December 31, 2017 2016 2015 Fair value, beginning of period $ 2,723 $ — $ 138 Issuance of 2017 Placement Warrants 3,373 — — Issuance of 2016 Placement Warrants — 2,726 — Change in fair value of Level 3 financial liabilities 16,598 (3 ) (45 ) Conversion of convertible preferred stock warrants to common stock warrants — — (93 ) Fair value of 2017 Placement Warrants at exercise (74 ) — — Fair value of 2016 Placement Warrants at exercise (200 ) — — Fair value, end of period $ 22,420 $ 2,723 $ —

Debt (Tables)

Debt (Tables)	12 Months Ended
	Dec. 31, 2017
Debt Disclosure [Abstract]
Scheduled Future Payments on Term Loan	The Company’s scheduled future payment on the CRG Term Loan at December 31, 2017 are as follows (in thousands): Year Ended December 31, 2018 $ 4,108 2019 4,299 2020 62,803 Total future payments 71,210 Less: amount representing interest and end-of-term facility fee (26,210 ) Total principal amount 45,000 Less: unamortized debt discount (496 ) Carrying value of long-term debt 44,504 Less: current portion — Long-term portion $ 44,504

Commitments and Contingencies (

Commitments and Contingencies (Tables)	12 Months Ended
	Dec. 31, 2017
Commitments And Contingencies Disclosure [Abstract]
Schedule of Future Minimum Lease Payments Under Non-cancellable Operating Lease Agreements	At December 31, 2017, the future minimum payments for the operating leases are as follows (in thousands): Year Ended December 31, 2018 $ 1,118 2019 1,039 Total future minimum payments $ 2,157

Common Stock Reserved for Iss34

Common Stock Reserved for Issuance (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Schedule of Common Stock Reserved for Future Issuance	The common stock reserved for future issuance at December 31, 2017 and 2016 was as follows: December 31, 2017 2016 Shares underlying outstanding stock options 8,592,747 6,127,291 Shares available for future stock option grants 969,783 2,168,391 Shares issuable upon settlement of restricted stock units outstanding 149,636 151,240 ESPP shares available for issuance 1,103,481 667,670 Warrant to purchase common stock 3,393,755 1,707,736 Total shares of common stock reserved 14,209,402 10,822,328

Warrants (Tables)

Warrants (Tables)	12 Months Ended
	Dec. 31, 2017
Equity [Abstract]
Summary of Assumptions using Black- Scholes Option Pricing Model to estimate fair value	The Company used the Black-Scholes option-pricing model to estimate the fair value of the convertible preferred stock warrant upon conversion with the following assumptions: Upon the Closing of the 2015 Common Stock Warrants: Expected term (in years) 5.0 Expected volatility (%) 31.8% Risk-free interest rate (%) 1.7% Expected dividend yield (%) 0% The fair value of the placement warrants was measured at their grant dates using the Black-Scholes pricing model and the following weighted average assumptions: Upon Issuance Common Stock Warrants: Expected term (in years) 5.0 Expected volatility (%) 31.8% Risk-free interest rate (%) 1.6% Expected dividend yield (%) 0% The fair value of the 2016 Placement Warrants of $9.9 million and $2.7 million at December 31, 2017 and 2016, respectively, was estimated using the Black-Scholes option pricing model and the following weighted-average assumptions: December 31, 2017 2016 2016 Placement Warrants: Expected term (in years) 5.7 6.7 Expected volatility (%) 62.1% 63.6% Risk-free interest rate (%) 2.2% 2.3% Expected dividend yield (%) 0% 0% The fair value of the 2017 Placement Warrants of $12.5 million at December 31, 2017 was estimated using the Black-Scholes option pricing model and the following weighted-average assumptions: December 31, 2017 2017 Placement Warrants: Expected term (in years) 6.1 Expected volatility (%) 62.3% Risk-free interest rate (%) 2.3% Expected dividend yield (%) 0%

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	12 Months Ended
	Dec. 31, 2017
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Summary of Company's Stock Option Activity and Related Information	A summary of the Company’s stock option activity and related information is as follows: Options Outstanding Shares Available for Grant Number of Stock Options Outstanding Weighted- Average Exercise Price Weighted- Average Remaining Contractual (Years) Aggregate Intrinsic Value (In Balance at December 31, 2016 2,168,391 6,127,291 2.60 7.3 7,800 Additional authorized 1,743,247 Granted (2,986,244 ) 2,986,244 5.65 Exercised — (420,377 ) 1.58 Cancelled 100,411 (100,411 ) 3.95 RSUs granted (56,022 ) — Balance at December 31, 2017 969,783 8,592,747 $ 3.69 7.4 $ 47,864 Vested and exercisable at December 31, 2017 5,011,207 $ 2.65 6.5 $ 33,130 Vested and expected to vest at December 31, 2017 8,303,413 $ 3.64 7.4 $ 46,655
Schedule of Weighted-Average Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Employee Stock Options at Grant Date	The fair value of employee stock options was estimated at the date of grant using a Black-Scholes option-pricing model with the following weighted-average assumptions: Year Ended December 31, 2017 2016 2015 Expected term (in years) 5.9 6.0 5.9 Expected volatility (%) 66.0% 67.1% 68.7% Risk-free interest rate (%) 2.1% 1.3% 1.8% Expected dividend yield (%) 0.0% 0.0% 0.0%
Summary of Stock-Based Compensation Expense	Total stock-based compensation expense recognized in the Company’s consolidated statements of operations and comprehensive loss is classified as follows (in thousands): Year Ended December 31, 2017 2016 2015 Research and development $ 952 $ 593 $ 262 Selling and marketing 303 120 50 General and administrative 4,064 2,194 754 Total stock-based compensation expense $ 5,319 $ 2,907 $ 1,066

Income Taxes (Tables)

Income Taxes (Tables)	12 Months Ended
	Dec. 31, 2017
Income Tax Disclosure [Abstract]
Schedule of Reconciliation of Differences Between Federal Income Tax Rate and Effective Tax Rate	The following reconciles the differences between income taxes computed at the federal income tax rate and the provision for income taxes: Year Ended December 31, 2017 2016 2015 Expected income tax benefit at the federal statutory rate 34.0 % 34.0 % 34.0 % State taxes, net of federal benefit 0.0 0.0 (0.8 ) Change in effective tax rate (54.1 ) 0.0 (0.9 ) Non-deductible items and other 0.5 (0.7 ) (0.5 ) Federal and state credits 0.5 0.6 (0.7 ) Change in valuation allowance 19.1 (33.9 ) (31.1 ) Total 0.0 % 0.0 % 0.0 %
Schedule of Deferred Tax Assets	The principal components of the Company’s net deferred tax assets consisted of the following at December 31, 2017 and 2016 (in thousands): Year Ended December 31, 2017 2016 Net operating loss carryforwards $ 61,049 $ 75,036 Research and development tax credits 3,731 2,131 Reserves and accruals 1,168 1,791 Other 6,611 4,594 Total deferred tax assets 72,559 83,552 Valuation allowance (72,559 ) (83,552 ) Net deferred tax assets $ — $ —
Schedule of Unrecognized Tax Benefits	At December 31, 2017 and 2016, the Company’s unrecognized tax benefits consist of the following: Year Ended December 31, 2017 2016 Unrecognized tax benefit, beginning of period $ 940 $ 742 Gross increases — current year tax positions 327 198 Gross increases — prior year tax positions 73 — Gross decreases — prior year tax positions (205 ) — Unrecognized tax benefit, end of period $ 1,135 $ 940

Net Loss per Share (Tables)

Net Loss per Share (Tables)	12 Months Ended
	Dec. 31, 2017
Earnings Per Share [Abstract]
Computation of Company's Basic and Diluted Net Loss Per Share	The following table sets forth the computation of the Company’s basic and diluted net loss per share for the periods presented (in thousands, except share and per share data): Year Ended December 31, 2017 2016 2015 Net loss $ (72,176 ) $ (50,636 ) $ (44,995 ) Weighted-average common shares used in computing net loss per share, basic and diluted 58,457,868 40,068,307 17,432,434 Net loss per share, basic and diluted $ (1.23 ) $ (1.26 ) $ (2.58 )
Anti-Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share	The following weighted-average common stock equivalents were excluded from the calculation of diluted net loss per share for the periods presented because including them would have had an anti-dilutive effect: Year Ended December 31, 2017 2016 2015 Convertible preferred stock (if converted) — — 16,558,330 Options to purchase common stock 7,914,067 6,181,015 5,032,768 Convertible preferred stock warrant — — 71,318 Common stock warrant 3,345,674 804,248 142,513 Restricted stock units 108,107 33,835 —

Segment and Geographic Inform39

Segment and Geographic Information (Tables)	12 Months Ended
	Dec. 31, 2017
Segment Reporting [Abstract]
Summary of Revenue by Geographic Area on the Customers' Location	The following table sets forth revenue by geographic area on the customers’ location (in thousands): Year Ended December 31, 2017 2016 2015 United States $ 11,506 $ 1,106 $ 5,332 UAE 5,675 — — Korea 5,504 182 4,988 Israel 5,309 — — China 4,680 — — Japan 753 10,375 — Netherlands 317 5,486 — Italy 298 5,088 — Rest of world — — 70 Total revenue $ 34,042 $ 22,237 $ 10,390

Background and Organization - A

Background and Organization - Additional Information (Detail) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Feb. 28, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Background And Organization [Line Items]
Net loss		$ (72,176)	$ (50,636)	$ (44,995)
Net cash used from operations		(70,053)	(28,156)	(39,849)
Cash and cash equivalents		$ 57,389	$ 14,198	$ 20,667	$ 11,129
Subsequent Event
Background And Organization [Line Items]
Proceeds from offering of common stock, gross	$ 59,100

Summary of Significant Accoun41

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Aug. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Oct. 31, 2015
Significant Accounting Policies [Line Items]
Restricted cash		$ 1,143,000	$ 1,143,000
Allowances for doubtful accounts		0	0
Inventory lower of cost and market adjustment		911,000	1,939,000	$ 2,578,000
Asset retirement obligation		334,000			$ 250,000
Impairment loss recognized		0	0	0
Deferred offering costs		$ 0	0
Wrote off deferred offering costs				$ 2,900,000
Service contract term		12 months
Distribution fee reclassified to deferred revenue		$ 23,389,000	10,433,000
Reserve for deferred costs of revenue		0	0
Excise tax on medical devices				2.30%
Deferred commission		3,500,000	2,600,000
Penalties and interest related to income taxes		0
Operating leases future minimum payments due		2,157,000
ASU No. 2016-18
Significant Accounting Policies [Line Items]
Restricted cash		$ 1,100,000	1,100,000
Itochu Corporation Agreement
Significant Accounting Policies [Line Items]
Remaining term of distribution agreement	8 years 6 months	8 years 6 months
License Cost
Significant Accounting Policies [Line Items]
Estimated useful life		3 years
Distribution Rights | Itochu Corporation Agreement
Significant Accounting Policies [Line Items]
Distribution fee reclassified to deferred revenue	$ 4,000,000	$ 4,000,000
Asset Retirement Obligation
Significant Accounting Policies [Line Items]
Accretion expenses		$ 40,000	36,000	$ 8,000
Minimum
Significant Accounting Policies [Line Items]
Property and equipment, useful life		2 years
Minimum | Patents
Significant Accounting Policies [Line Items]
Estimated useful life		5 years
Maximum
Significant Accounting Policies [Line Items]
Property and equipment, useful life		15 years
Maximum | Patents
Significant Accounting Policies [Line Items]
Estimated useful life		7 years
Irrevocable Standby Letters of Credit
Significant Accounting Policies [Line Items]
Letters of credit drawn, amount		$ 0	0
Collateral for Letters of Credit
Significant Accounting Policies [Line Items]
Restricted cash		900,000	$ 900,000
Collateral For Credit Card
Significant Accounting Policies [Line Items]
Restricted cash		$ 200,000

Summary of Significant Accoun42

Summary of Significant Accounting Policies - Schedule of Customers Representing Greater than 10% of Accounts Receivable and Revenue (Detail) - Customer Concentration Risk	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Revenue | Customer A
Concentration Risk [Line Items]
Percentage of concentration risk	17.00%
Revenue | Customer B
Concentration Risk [Line Items]
Percentage of concentration risk	17.00%
Revenue | Customer C
Concentration Risk [Line Items]
Percentage of concentration risk	16.00%		48.00%
Revenue | Customer D
Concentration Risk [Line Items]
Percentage of concentration risk	16.00%
Revenue | Customer E
Concentration Risk [Line Items]
Percentage of concentration risk	14.00%
Revenue | Customer F
Concentration Risk [Line Items]
Percentage of concentration risk	10.00%
Revenue | Customer H
Concentration Risk [Line Items]
Percentage of concentration risk		47.00%
Revenue | Customer I
Concentration Risk [Line Items]
Percentage of concentration risk		25.00%
Revenue | Customer J
Concentration Risk [Line Items]
Percentage of concentration risk		23.00%
Revenue | Customer K
Concentration Risk [Line Items]
Percentage of concentration risk			43.00%
Accounts Receivable | Customer D
Concentration Risk [Line Items]
Percentage of concentration risk	24.00%
Accounts Receivable | Customer E
Concentration Risk [Line Items]
Percentage of concentration risk	16.00%
Accounts Receivable | Customer G
Concentration Risk [Line Items]
Percentage of concentration risk	36.00%
Accounts Receivable | Customer H
Concentration Risk [Line Items]
Percentage of concentration risk		49.00%
Accounts Receivable | Customer J
Concentration Risk [Line Items]
Percentage of concentration risk		41.00%

Summary of Significant Accoun43

Summary of Significant Accounting Policies - Schedule of Depreciation and Amortization Periods for Property and Equipment (Detail)	12 Months Ended
	Dec. 31, 2017
Minimum
Property Plant And Equipment [Line Items]
Property and equipment, useful life	2 years
Maximum
Property Plant And Equipment [Line Items]
Property and equipment, useful life	15 years
Prototype | Minimum
Property Plant And Equipment [Line Items]
Property and equipment, useful life	2 years
Prototype | Maximum
Property Plant And Equipment [Line Items]
Property and equipment, useful life	10 years
Machinery and Equipment | Minimum
Property Plant And Equipment [Line Items]
Property and equipment, useful life	5 years
Machinery and Equipment | Maximum
Property Plant And Equipment [Line Items]
Property and equipment, useful life	15 years
Furniture and Fixtures | Minimum
Property Plant And Equipment [Line Items]
Property and equipment, useful life	5 years
Furniture and Fixtures | Maximum
Property Plant And Equipment [Line Items]
Property and equipment, useful life	10 years
Software
Property Plant And Equipment [Line Items]
Property and equipment, useful life	3 years
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and Equipment, Estimated Useful Life	Lesser of estimated useful life or remaining lease term

Merger - Additional Information

Merger - Additional Information (Details) $ / shares in Units, $ in Millions	Jul. 23, 2015USD ($)$ / sharesshares	Dec. 31, 2017$ / sharesshares	Dec. 31, 2015	Dec. 31, 2016$ / sharesshares	Jul. 31, 2015shares
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
Percentage of common stock on diluted basis	12.30%
Private Placement | Investor
Business Acquisition [Line Items]
Private placement, value | $	$ 17
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

Balance Sheet Components - Sche

Balance Sheet Components - Schedule of Property and Equipment (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 25,898	$ 23,727
Less: accumulated depreciation and amortization	(14,334)	(12,167)
Property and equipment, net	11,564	11,560
Prototype
Property Plant And Equipment [Line Items]
Property and equipment, gross	11,929	6,405
Machine and Equipment
Property Plant And Equipment [Line Items]
Property and equipment, gross	7,831	6,057
Leasehold Improvements
Property Plant And Equipment [Line Items]
Property and equipment, gross	4,438	4,371
Furniture and Fixtures
Property Plant And Equipment [Line Items]
Property and equipment, gross	558	368
Software
Property Plant And Equipment [Line Items]
Property and equipment, gross	1,142	1,028
Construction In Progress
Property Plant And Equipment [Line Items]
Property and equipment, gross	$ 0	$ 5,498

Balance Sheet Components - Addi

Balance Sheet Components - Additional Information (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Balance Sheet Related Disclosures [Abstract]
Depreciation and amortization	$ 2,200	$ 1,600	$ 1,100
Amortization of intangible assets	$ 19	$ 115	$ 168

Balance Sheet Components - Summ

Balance Sheet Components - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 616	$ 616
Accumulated amortization	(538)	(519)
Intangible assets, net	78	97
License Cost
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	512	512
Patents
Finite Lived Intangible Assets [Line Items]
Intangible assets, gross	$ 104	$ 104

Balance Sheet Components - Su48

Balance Sheet Components - Summary of Estimated Future Amortization Expense (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Balance Sheet Related Disclosures [Abstract]
2,018	$ 19
2,019	19
2,020	19
2,021	10
2,022	3
Thereafter	8
Intangible assets, net	$ 78	$ 97

Balance Sheet Components - Sc49

Balance Sheet Components - Schedule of Accrued Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Payables And Accruals [Abstract]
Accrued payroll and related benefits	$ 3,944	$ 4,274
Accrued accounts payable	2,671	1,202
Tax payable	149	13
Accrued legal and accounting	322	509
Other	121	336
Total accrued liabilities	$ 7,207	$ 6,334

Balance Sheet Components - Sc50

Balance Sheet Components - Schedule of Deferred Revenue (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 23,389	$ 10,433
Less: current portion of deferred revenue	(20,151)	(6,515)
Noncurrent portion of deferred revenue	3,238	3,918
Product
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	18,861	5,050
Services
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	1,182	1,561
Distribution Rights
Deferred Revenue Arrangement [Line Items]
Total deferred revenue	$ 3,346	$ 3,822

Fair Value of Financial Instr51

Fair Value of Financial Instruments - Additional Information (Detail) - USD ($)	1 Months Ended	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Convertible preferred stock warrant liability				$ 93,000
Change in fair value of Level 3 financial liabilities		$ (16,598,000)	$ 3,000	$ 45,000
2016 Placement Warrant
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Placement warrants exercised	25,014
Aggregate fair value of warrants upon exercise		$ 200,000
Placement warrants outstanding	1,355,641	1,355,641
2017 Placement Warrants
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Placement warrants exercised	9,389
Aggregate fair value of warrants upon exercise		$ 74,000
Placement warrants outstanding	1,711,123	1,711,123
Two Thousand Sixteen And Two Thousand Seventeen Private Placement Warrants
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Aggregate fair value of warrants upon exercise	$ 274,000
Change in fair value of Level 3 financial liabilities		$ (16,600,000)	$ 3,000
Transfers between Level 1 to Level 2	0	0
Transfers between Level 2 to Level 1	$ 0	0
Transfers into or out of Level 3		$ 0

Fair Value of Financial Instr52

Fair Value of Financial Instruments - Schedule of Fair Value of Financial Liabilities (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	$ 22,420	$ 2,723
Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0
Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0
Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	22,420
2017 Placement Warrants Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	12,487
2017 Placement Warrants Liability | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0
2017 Placement Warrants Liability | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0
2017 Placement Warrants Liability | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	12,487
2016 Placement Warrants Liability
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	9,933	2,723
2016 Placement Warrants Liability | Level 1
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0	0
2016 Placement Warrants Liability | Level 2
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	0	0
2016 Placement Warrants Liability | Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Total Warrant Liability	$ 9,933	$ 2,723

Fair Value of Financial Instr53

Fair Value of Financial Instruments - Summary of Changes in Fair Value of Level 3 Financial Liabilities (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Fair value, beginning of period	$ 2,723	$ 0	$ 138
Change in fair value of Level 3 financial liabilities	16,598	(3)	(45)
Conversion of convertible preferred stock warrants to common stock warrants	0	0	(93)
Fair value, end of period	22,420	2,723	0
2017 Placement Warrants Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Issuance of Placement Warrants	3,373
Fair value of Placement Warrants at exercise	(74)
2016 Placement Warrants Liability
Fair Value Liabilities Measured On Recurring Basis Unobservable Input Reconciliation [Line Items]
Issuance of Placement Warrants	0	$ 2,726	$ 0
Fair value of Placement Warrants at exercise	$ (200)

Debt - Additional Information (

Debt - Additional Information (Detail) - USD ($)	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. 1, 2017
Beginning period for monthly principal and interest payments							Jan. 1, 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%

Debt - Scheduled Future Payment

Debt - Scheduled Future Payments on Term Loan (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Debt Instrument [Line Items]
Long-term portion	$ 44,504	$ 44,290
CRG Term Loan
Debt Instrument [Line Items]
2,018	4,108
2,019	4,299
2,020	62,803
Total future payments	71,210
Less: amount representing interest and end-of-term facility fee	(26,210)
Total principal amount	45,000
Less: unamortized debt discount	(496)
Carrying value of long-term debt	44,504
Less: current portion	0
Long-term portion	$ 44,504

Commitments and Contingencies -

Commitments and Contingencies - Schedule of Future Minimum Lease Payments Under Non-cancellable Operating Lease Agreements (Detail) $ in Thousands	Dec. 31, 2017USD ($)
Operating Leases Future Minimum Payments Due [Abstract]
2,018	$ 1,118
2,019	1,039
Total future minimum payments	$ 2,157

Commitments and Contingencies57

Commitments and Contingencies - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments And Contingencies Disclosure [Abstract]
Rent expense	$ 1,300,000	$ 1,300,000	$ 1,300,000
Purchase commitments	$ 0	$ 0

Licensing Agreement- Additional

Licensing Agreement- Additional Information (Detail) - Licensing Agreements - USD ($)	1 Months Ended	3 Months Ended	12 Months Ended
	Dec. 31, 2004	Mar. 31, 2014	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Licenses Agreements [Line Items]
Common Stock granted in exchange for licensing	33,652
Milestone description			ViewRay Technologies, Inc. met all of the product development and commercialization milestones at December 31, 2013 and started to make quarterly royalty payments in 2014.
Percentage of royalty payment based on net sale			1.00%
Cost of Sales
Licenses Agreements [Line Items]
Royalty Expense			$ 274,400	$ 206,000	$ 49,000
General and Administrative
Licenses Agreements [Line Items]
Royalty Expense			$ 25,000	$ 57,000	$ 102,000
Minimum
Licenses Agreements [Line Items]
Quarterly royalty payment		$ 50,000

Distribution Agreement - Additi

Distribution Agreement - Additional Information (Detail) $ in Thousands	1 Months Ended		12 Months Ended
	Aug. 31, 2016USD ($)	Dec. 31, 2014USD ($)Installment	Dec. 31, 2017USD ($)	Dec. 31, 2016USD ($)	Dec. 31, 2015USD ($)	Dec. 31, 2014USD ($)
Marketing Agreement [Line Items]
Distribution fee reclassified to deferred revenue			$ 23,389	$ 10,433
Distribution rights revenue			$ 475	178	$ 0
Itochu Corporation Agreement
Marketing Agreement [Line Items]
Distribution agreement term		10 years
Distribution fees		$ 4,000
Number of installments | Installment		3
Remaining term of distribution agreement	8 years 6 months		8 years 6 months
Distribution rights revenue			$ 475	$ 178
Itochu Corporation Agreement | Distribution Rights
Marketing Agreement [Line Items]
Distribution fee reclassified to deferred revenue	$ 4,000		$ 4,000
Itochu Corporation Agreement | First Installment
Marketing Agreement [Line Items]
Distribution fees		$ 1,000
Itochu Corporation Agreement | Second Installment
Marketing Agreement [Line Items]
Distribution fees		1,000
Itochu Corporation Agreement | Third Installment
Marketing Agreement [Line Items]
Distribution fees		$ 2,000
Distribution fees payment	$ 2,000
Itochu Corporation Agreement | First and Second Installment
Marketing Agreement [Line Items]
Distribution fees payment					$ 2,000	$ 2,000

Equity Financing - Additional I

Equity Financing - Additional Information (Detail) - USD ($)	Jul. 23, 2015	Oct. 31, 2017	Jan. 31, 2017	Sep. 30, 2016	Aug. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Apr. 30, 2017
2017 Placement Warrants
Subsidiary Sale Of Stock [Line Items]
Warrants to purchase common stock, shares			1,720,512
Warrant exercise price			$ 3.17
Warrant exercisable date			Jul. 31, 2017
Warrant expiration date			Jan. 31, 2024
2016 Placement Warrants Liability
Subsidiary Sale Of Stock [Line Items]
Warrants to purchase common stock, shares				1,380,745	1,380,745
Warrant exercise price				$ 2.95	$ 2.95
Warrant expiration period				7 years	7 years
Private Placement
Subsidiary Sale Of Stock [Line Items]
Private placement, common shares	5,884,504
Proceed from private placement and equity issuances, gross			$ 26,100,000	$ 13,800,000		$ 26,100,000	$ 13,800,000
Private Placement | Common Stock
Subsidiary Sale Of Stock [Line Items]
Private placement, common shares			8,602,589	4,602,506
Stock issued during period						8,602,589	4,602,506	5,884,504
At The Market Offering Program
Subsidiary Sale Of Stock [Line Items]
Proceeds from offering of common stock, gross						$ 40,126,000	$ 0	$ 0
Compensation percentage pertaining to gross sales price per share sold						3.00%
Stock issued during period						0
Average market price per share						$ 6.10
At The Market Offering Program | Maximum
Subsidiary Sale Of Stock [Line Items]
Maximum aggregate offering price			$ 75,000,000						$ 100,000,000
Maximum common stock saleable value			$ 25,000,000						$ 25,000,000
At The Market Offering Program | Common Stock
Subsidiary Sale Of Stock [Line Items]
Stock issued during period						6,575,062
2017 Direct Registered Offering
Subsidiary Sale Of Stock [Line Items]
Proceeds from offering of common stock, gross		$ 50,000,000
2017 Direct Registered Offering | Common Stock
Subsidiary Sale Of Stock [Line Items]
Private placement, common shares		8,382,643

Common Stock Reserved for Iss61

Common Stock Reserved for Issuance - Schedule of Common Stock Reserved for Future Issuance (Detail) - shares	Dec. 31, 2017	Dec. 31, 2016
Class Of Stock [Line Items]
Total shares of common stock reserved	14,209,402	10,822,328
Shares available for future stock option grants
Class Of Stock [Line Items]
Total shares of common stock reserved	969,783	2,168,391
ESPP shares available for issuance
Class Of Stock [Line Items]
Total shares of common stock reserved	1,103,481	667,670
Warrant to purchase common stock
Class Of Stock [Line Items]
Total shares of common stock reserved	3,393,755	1,707,736
Options To Purchase Common Stock
Class Of Stock [Line Items]
Total shares of common stock reserved	8,592,747	6,127,291
Shares issuable upon settlement of restricted stock units outstanding
Class Of Stock [Line Items]
Total shares of common stock reserved	149,636	151,240

Convertible Preferred Stock - A

Convertible Preferred Stock - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended
	Feb. 28, 2015	Jan. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2015
Convertible Preferred Stock [Line Items]
Number of convertible preferred stock converted to common stock						30,381,987
Preferred stock conversion rate						100.00%
Preferred stock, shares issued			0	0
Preferred stock, shares outstanding			0	0
Series C Convertible Preferred Stock
Convertible Preferred Stock [Line Items]
Convertible preferred stock, shares issued	2,564,652	162,407
Stock price	$ 5.84	$ 5.84
Issuance of convertible preferred stock	$ 15,000	$ 950
Convertible Preferred Stock
Convertible Preferred Stock [Line Items]
Preferred stock, shares issued			0	0	0
Preferred stock, shares outstanding			0	0	0

Warrants - Additional Informati

Warrants - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	Aug. 22, 2016	Dec. 31, 2017	Jan. 31, 2017	Sep. 30, 2016	Aug. 31, 2016	Aug. 31, 2015	Jul. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2013
Common Stock Warrants [Line Items]
(Gain) loss related to change in fair value								$ 16,598	$ (3)	$ (45)
Convertible preferred stock warrant liability							$ 93			93
Fair value of warrants		$ 22,420						22,420	2,723
Adjustments to additional paid In capital warrant exercised		274
Private Placement
Common Stock Warrants [Line Items]
Proceed from private placement and equity issuances, gross			$ 26,100	$ 13,800				26,100	13,800
Fair value of warrants upon issuance under Private Placement	$ 2,700
2015 Placement Common Stock Warrants
Common Stock Warrants [Line Items]
Estimated fair value of the warrants issued to placement agents										$ 316
2015 Placement Common Stock Warrants | Insiders
Common Stock Warrants [Line Items]
Warrants issued						198,760	198,760
Exercise price						$ 5	$ 5
Common stock warrants, expiry term						5 years	5 years
2016 Placement Warrant
Common Stock Warrants [Line Items]
Warrants issued				1,380,745	1,380,745
Exercise price				$ 2.95	$ 2.95
(Gain) loss related to change in fair value								$ 7,400	$ (3)
Common stock warrants, expiry term				7 years	7 years
Expected term (in years)								5 years 8 months 12 days	6 years 8 months 12 days
Expected volatility								62.10%	63.60%
Risk-free interest rate								2.20%	2.30%
Expected dividend yield								0.00%	0.00%
Fair value of warrants		$ 9,933						$ 9,933	$ 2,723
Class of warrant exercised		25,104						25,104
Placement warrants outstanding		1,355,641						1,355,641
2016 Placement Warrants
Common Stock Warrants [Line Items]
Expected term (in years)	7 years
Expected volatility	61.60%
Risk-free interest rate	1.40%
Expected dividend yield	0.00%
2017 Placement Warrants
Common Stock Warrants [Line Items]
Warrants issued			1,720,512
Exercise price			$ 3.17
(Gain) loss related to change in fair value								$ 9,200
Fair value of warrants upon issuance under Private Placement			$ 3,400
Expected term (in years)			7 years					6 years 1 month 6 days
Expected volatility			62.90%					62.30%
Risk-free interest rate			2.20%					2.30%
Expected dividend yield			0.00%					0.00%
Fair value of warrants		$ 12,487						$ 12,487
Warrant exercisable date			Jul. 31, 2017
Warrant expiration date			Jan. 31, 2024
Class of warrant exercised		9,389						9,389
Placement warrants outstanding		1,711,123						1,711,123
Term Loan | Series C Convertible Preferred Stock
Common Stock Warrants [Line Items]
Warrants issued							128,231				128,231
Exercise price											$ 5.84
Common stock warrants, expiration date											Dec. 16, 2023

Warrants - Summary of Assumptio

Warrants - Summary of Assumptions to Use Option Pricing Model (Detail)	Jul. 23, 2015	Jan. 31, 2017	Aug. 31, 2015	Dec. 31, 2017	Dec. 31, 2016
2016 Placement Warrant
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Expected term (in years)				5 years 8 months 12 days	6 years 8 months 12 days
Expected volatility				62.10%	63.60%
Risk-free interest rate				2.20%	2.30%
Expected dividend yield				0.00%	0.00%
2017 Placement Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Expected term (in years)		7 years		6 years 1 month 6 days
Expected volatility		62.90%		62.30%
Risk-free interest rate		2.20%		2.30%
Expected dividend yield		0.00%		0.00%
Series C Convertible Preferred Stock Warrant
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Expected term (in years)	5 years
Expected volatility	31.80%
Risk-free interest rate	1.70%
Expected dividend yield	0.00%
Common Stock Warrants
Fair Value Inputs Liabilities Quantitative Information [Line Items]
Expected term (in years)			5 years
Expected volatility			31.80%
Risk-free interest rate			1.60%
Expected dividend yield			0.00%

Stock-Based Compensation - Addi

Stock-Based Compensation - Additional Information (Detail) - USD ($)	1 Months Ended				12 Months Ended
	Dec. 31, 2017	Nov. 30, 2017	Dec. 31, 2016	Sep. 30, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015	Jul. 31, 2015	Jul. 23, 2015
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock option grant, description					Options granted may be either incentive stock options or non-statutory stock options.
Common stock reserved for issuance	14,209,402		10,822,328		14,209,402	10,822,328
Grant date fair value of options granted, per share					$ 3.38	$ 2.72	$ 3.13
Grant date fair value of options vested					$ 4,800,000	$ 2,400,000	$ 782,000
Aggregate intrinsic value of options exercised					2,600,000	2,300,000
Unrecognized compensation cost	$ 9,900,000				$ 9,900,000
Weighted average period for recognition of compensation costs					2 years 8 months 12 days
RSUs Granted					56,022
Stock based compensation expenses					$ 5,319,000	2,907,000	1,066,000
Stock-based compensation expense capitalized					0	0	0
General and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expenses					$ 4,064,000	$ 2,194,000	$ 754,000
Restricted Stock Units (RSUs)
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance	149,636		151,240		149,636	151,240
Weighted average grant date fair value of RSUs granted					$ 8.02	$ 3.52	$ 0
Stock based compensation expenses					$ 0	$ 0	$ 0
Restricted Stock Units (RSUs) | General and Administrative Expenses
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock based compensation expenses					$ 449,000	$ 532,000	$ 0
Restricted Stock Units (RSUs) | Board of Directors
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSUs Granted	0	43,554		112,578
RSUs Released	18,964	0		0
Restricted Stock Units (RSUs) | Executive Officers
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSUs Granted		12,468	18,017
Restricted Stock Units (RSUs) | Consultant
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
RSUs Granted			20,645
Two Thousand Eight Stock Option Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of stock option plan					10 years
Exercisable period of stock option plan					4 years
Two Thousand Eight Stock Option Plan | Nonstatutory Options | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of fair value of common stock, percentage					85.00%
Two Thousand Eight Stock Option Plan | Ten Percent Stockholder
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Expiration period of stock option plan					5 years
Two Thousand Eight and Two Thousand Fifteen Stock Option Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Voting power Percentage					10.00%
Two Thousand Eight and Two Thousand Fifteen Stock Option Plan | Ten Percent Stockholder | Minimum
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Exercise price of fair value of common stock, percentage					110.00%
2015 Employee Stock Purchase Plan
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Common stock reserved for issuance								667,670	285,621
Shares issued under ESPP					0	0

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Company's Stock Option Activity and Related Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Shares Available for Grant
Shares Available for Grant, Beginning balance	2,168,391
Shares Available for Grant, Additional authorized	1,743,247
Shares Available for Grant, Granted	(2,986,244)
Shares Available for Grant, Cancelled	100,411
Shares Available for Grant, RSUs granted	(56,022)
Shares Available for Grant, Ending balance	969,783	2,168,391
Number of Stock Options Outstanding
Number of Stock Options Outstanding, Beginning balance	6,127,291
Number of Stock Options Outstanding, Granted	2,986,244
Number of Stock Options Outstanding, Exercised	(420,377)
Number of Stock Options Outstanding, Cancelled	(100,411)
Number of Stock Options Outstanding, Ending balance	8,592,747	6,127,291
Number of Stock Options Outstanding, Vested and exercisable	5,011,207
Number of Stock Options Outstanding, Vested and expected to vest	8,303,413
Weighted- Average Exercise Price
Weighted- Average Exercise Price, Beginning balance	$ 2.60
Weighted- Average Exercise Price, Granted	5.65
Weighted- Average Exercise Price, Exercised	1.58
Weighted- Average Exercise Price, Cancelled	3.95
Weighted- Average Exercise Price, Ending balance	3.69	$ 2.60
Weighted- Average Exercise Price, Vested and exercisable	2.65
Weighted- Average Exercise Price, Vested and expected to vest	$ 3.64
Weighted- Average Remaining Contractual Life (Years)
Options Outstanding, Weighted- Average Remaining Contractual Life (Years)	7 years 4 months 24 days	7 years 3 months 19 days
Weighted- Average Remaining Contractual Life (Years), Vested and exercisable	6 years 6 months
Weighted- Average Remaining Contractual Life (Years), Vested and expected to vest	7 years 4 months 24 days
Aggregate Intrinsic Value
Aggregate Intrinsic Value	$ 47,864	$ 7,800
Aggregate Intrinsic Value, Vested and exercisable	33,130
Aggregate Intrinsic Value, Vested and expected to vest	$ 46,655

Stock-Based Compensation - Sche

Stock-Based Compensation - Schedule of Weighted-Average Assumptions Used in Black-Scholes Option-Pricing Model to Estimate Fair Value of Employee Stock Options at Grant Date (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Expected term (in years)	5 years 10 months 24 days	6 years	5 years 10 months 24 days
Expected volatility (%)	66.00%	67.10%	68.70%
Risk-free interest rate (%)	2.10%	1.30%	1.80%
Expected dividend yield (%)	0.00%	0.00%	0.00%

Stock-Based Compensation - Su68

Stock-Based Compensation - Summary of Stock-Based Compensation Expense (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 5,319	$ 2,907	$ 1,066
Research and Development
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	952	593	262
Selling and Marketing
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	303	120	50
General and Administrative
Employee Service Share Based Compensation Allocation Of Recognized Period Costs [Line Items]
Stock-based compensation expense	$ 4,064	$ 2,194	$ 754

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Taxes [Line Items]
Federal statutory tax rate		34.00%	34.00%	34.00%
Change in deferred tax assets due to tax cuts and jobs act of 2017		$ (38.7)
Change in valuation allowance due to tax cuts and jobs act of 2017		(38.7)
Deferred Tax Valuation allowance increase (decrease)		(11)	$ 17.4
Federal [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		$ 266.3
Operating loss carryforwards, expiration date		Dec. 31, 2024
Federal [Member] | Research Tax Credit Carryforward
Income Taxes [Line Items]
Tax credit carryforwards		$ 3.8
Tax credit carryforwards, expiration date		Dec. 31, 2024
State and Local Jurisdiction [Member]
Income Taxes [Line Items]
Net operating loss carryforwards		$ 144.8
Operating loss carryforwards, expiration date		Dec. 31, 2019
State and Local Jurisdiction [Member] | Research Tax Credit Carryforward
Income Taxes [Line Items]
Tax credit carryforwards		$ 1.3
Tax credit carryforwards, expiration date		Dec. 31, 2024
Maximum
Income Taxes [Line Items]
Federal statutory tax rate		35.00%
Scenario Plan [Member]
Income Taxes [Line Items]
Federal statutory tax rate	21.00%

Income Taxes - Income Tax Recon

Income Taxes - Income Tax Reconciliation (Detail)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Effective Income Tax Rate Continuing Operations Tax Rate Reconciliation [Abstract]
Expected income tax benefit at the federal statutory rate	34.00%	34.00%	34.00%
State taxes, net of federal benefit	0.00%	0.00%	(0.80%)
Change in effective tax rate	(54.10%)	0.00%	(0.90%)
Non-deductible items and other	0.50%	(0.70%)	(0.50%)
Federal and state credits	0.50%	0.60%	(0.70%)
Change in valuation allowance	19.10%	(33.90%)	(31.10%)
Total	0.00%	0.00%	0.00%

Income Taxes - Deferred Income

Income Taxes - Deferred Income Tax (Detail) - USD ($) $ in Thousands	Dec. 31, 2017	Dec. 31, 2016
Deferred Tax Assets, Net [Abstract]
Net operating loss carryforwards	$ 61,049	$ 75,036
Research and development tax credits	3,731	2,131
Reserves and accruals	1,168	1,791
Other	6,611	4,594
Total deferred tax assets	72,559	83,552
Valuation allowance	(72,559)	(83,552)
Net deferred tax assets	$ 0	$ 0

Income Taxes - Unrecognized Tax

Income Taxes - Unrecognized Tax Benefits (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Unrecognized tax benefit, beginning of period	$ 940	$ 742
Gross increases — current year tax positions	327	198
Gross increases — prior year tax positions	73	0
Gross decreases — prior year tax positions	(205)	0
Unrecognized tax benefit, end of period	$ 1,135	$ 940

Employee Benefits - Additional

Employee Benefits - Additional information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Compensation And Retirement Disclosure [Abstract]
Description of Defined Contribution Plan	The Company has a 401(k) Plan which covers its eligible employees. The 401(k) Plan permits the participants to defer a portion of their compensation in accordance with the provisions of Section 401(k) of the IRC. At its discretion, the Company can match a portion of the participants’ contributions or make profit-sharing contributions
Defined Contribution Plan, Employer Discretionary Contribution Amount	$ 0	$ 0	$ 0

Net Loss Per Share - Computatio

Net Loss Per Share - Computation of Company's Basic and Diluted Net Loss Per Share (Detail) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Earnings Per Share [Abstract]
Net loss	$ (72,176)	$ (50,636)	$ (44,995)
Weighted-average common shares used in computing net loss per share, basic and diluted	58,457,868	40,068,307	17,432,434
Net loss per share, basic and diluted	$ (1.23)	$ (1.26)	$ (2.58)

Net Loss Per Share - Anti-Dilut

Net Loss Per Share - Anti-Dilutive Securities Excluded from Calculation of Diluted Net Loss Per Share (Detail) - shares	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Convertible Preferred Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share			16,558,330
Options To Purchase Common Stock
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	7,914,067	6,181,015	5,032,768
Convertible Preferred Stock Warrant
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share			71,318
Common Stock Warrant
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	3,345,674	804,248	142,513
Restricted Stock Units (RSUs)
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive securities excluded from calculation of diluted net loss per share	108,107	33,835

Segment and Geographic Inform76

Segment and Geographic Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2017Segment
Segment Reporting [Abstract]
Number of reportable segments	1

Segment and Geographic Inform77

Segment and Geographic Information - Summary of Revenue by Geographic Area on the Customers' Location (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Entity Wide Revenue Major Customer [Line Items]
Total revenue	$ 34,042	$ 22,237	$ 10,390
Reportable Geographical Components | United States
Entity Wide Revenue Major Customer [Line Items]
Total revenue	11,506	1,106	5,332
Reportable Geographical Components | UAE
Entity Wide Revenue Major Customer [Line Items]
Total revenue	5,675	0	0
Reportable Geographical Components | Korea
Entity Wide Revenue Major Customer [Line Items]
Total revenue	5,504	182	4,988
Reportable Geographical Components | Israel
Entity Wide Revenue Major Customer [Line Items]
Total revenue	5,309	0	0
Reportable Geographical Components | China
Entity Wide Revenue Major Customer [Line Items]
Total revenue	4,680	0	0
Reportable Geographical Components | Japan
Entity Wide Revenue Major Customer [Line Items]
Total revenue	753	10,375	0
Reportable Geographical Components | Netherlands
Entity Wide Revenue Major Customer [Line Items]
Total revenue	317	5,486	0
Reportable Geographical Components | Italy
Entity Wide Revenue Major Customer [Line Items]
Total revenue	298	5,088	0
Reportable Geographical Components | Rest of World
Entity Wide Revenue Major Customer [Line Items]
Total revenue	$ 0	$ 0	$ 70

Related Party Transactions - Ad

Related Party Transactions - Additional Information (Detail) - Sales Consulting Agreement [Member] - Investment Manager of Investment Company $ in Millions	1 Months Ended
	Jan. 31, 2017USD ($)
Related Party Transaction [Line Items]
Related party, agreement term	1 year
Related party, total consideration	$ 1.3

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - Subsequent Event $ / shares in Units, shares in Millions, $ in Millions	1 Months Ended
	Feb. 28, 2018USD ($)$ / sharesshares
Subsequent Event [Line Items]
Warrants to purchase common stock, shares	1.4
Proceed from private placement and equity issuances, gross | $	$ 59.1
Exercise price | $ / shares	$ 8.31
Warrant expiration period	7 years
Common Stock
Subsequent Event [Line Items]
Stock issued during period	4.1
Series A Convertible Preferred Stock
Subsequent Event [Line Items]
Stock issued during period	3