Arbutus Biopharma (ABUS) 10-Q 6 Nov 19 2019 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2019	Oct. 31, 2019
Document and Entity Information [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2019
Entity Registrant Name	Arbutus Biopharma Corp
Entity Central Index Key	0001447028
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Common Stock, Shares Outstanding		56,850,172
Entity Current Reporting Status	Yes
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q3
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Small Business	true

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets - USD ($)	Sep. 30, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 90,082,000	$ 36,942,000
Short-term investments	0	87,675,000
Accounts receivable	2,488,000	1,431,000
Prepaid expenses and other current assets	1,771,000	3,181,000
Total current assets	94,341,000	129,229,000
Investment in Genevant	10,969,000	22,224,000
Property and equipment, net accumulated depreciation $8,612 (December 31, 2018: $7,090)	9,150,000	10,145,000
Right of use asset (note 5)	2,817,000	0
Intangible assets	0	43,836,000
Goodwill	0	22,471,000
Total assets	117,277,000	227,905,000
Current liabilities:
Accounts payable and accrued liabilities (note 7)	8,199,000	9,429,000
Site consolidation accrual (note 8)	203,000	1,331,000
Liability-classified options (note 3)	86,000	479,000
Lease liability, current (note 5)	329,000	0
Total current liabilities	8,817,000	11,239,000
Liability related to sale of future royalties (note 9)	18,675,000	0
Deferred rent and inducements, non-current	0	645,000
Contingent consideration (notes 3 and 10)	3,005,000	3,126,000
Lease liability, non-current (note 5)	3,143,000	0
Deferred tax liability (note 6)	0	12,661,000
Total liabilities	33,640,000	27,671,000
Stockholders’ equity:
Preferred shares, Authorized - 1,164,000 with no par value, Issued and outstanding: 1,164,000 (December 31, 2018 - 1,164,000)	134,405,000	126,136,000
Common shares, Authorized - unlimited number with no par value, Issued and outstanding: 56,850,172 (December 31, 2018 - 55,518,800)	884,623,000	879,405,000
Additional paid-in capital	55,385,000	48,084,000
Deficit	(942,559,000)	(805,221,000)
Accumulated other comprehensive loss	(48,217,000)	(48,170,000)
Total stockholders' equity	83,637,000	200,234,000
Total liabilities and stockholders' equity	$ 117,277,000	$ 227,905,000

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Accumulated of property, plant, and equipment	$ 8,612	$ 7,090
Preferred stock, no par value (in USD per share)
Preferred stock, shares authorized (in shares)	1,164,000	1,164,000
Preferred stock, shares issued (in shares)	1,164,000	1,164,000
Preferred stock, shares outstanding (in shares)	1,164,000	1,164,000
Common shares, no par value (in USD per share)
Common shares, shares issued (in shares)	56,850,172	55,518,800
Common shares, shares outstanding (in shares)	56,850,172	55,518,800

Condensed Consolidated Statemen

Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Revenue
Revenue	$ 3,061	$ 1,587	$ 4,393	$ 4,267
Operating expenses
Research and development	17,731	16,566	45,183	46,871
General and administrative	3,249	2,631	15,850	10,075
Depreciation	507	497	1,521	1,677
Site consolidation (note 8)	182	(492)	33	3,710
Impairment of intangible assets (note 6)	43,836	14,811	43,836	14,811
Impairment of goodwill (note 6)	22,471	0	22,471	0
Arbitration (note 10)	6,486	0	6,486	0
Total operating expenses	94,462	34,013	135,380	77,144
Loss from operations	(91,401)	(32,426)	(130,987)	(72,877)
Other income (loss)
Interest income	503	756	1,709	2,319
Interest expense (note 9)	(1,100)	0	(1,114)	(104)
Foreign exchange gain (loss)	(25)	145	43	(740)
Gain on investment (note 4)	0	0	0	24,884
Equity investment loss (note 4)	(3,512)	(2,838)	(11,497)	(2,838)
Change in fair value of contingent consideration (notes 3 and 10)	376	5,608	121	6,263
Total other income (loss)	(3,758)	3,671	(10,738)	29,784
Loss before income taxes	(95,159)	(28,755)	(141,725)	(43,093)
Income tax benefit (note 6)	12,656	4,282	12,656	4,282
Net loss	(82,503)	(24,473)	(129,069)	(38,811)
Items applicable to preferred shares:
Accrual of coupon on convertible preferred shares	(2,792)	(2,567)	(8,269)	(7,444)
Net loss attributable to common shareholders (note 2)	$ (85,295)	$ (27,040)	$ (137,338)	$ (46,255)
Net loss attributable to common shareholders, per share
Basic and dilutive (in USD per share)	$ (1.50)	$ (0.49)	$ (2.43)	$ (0.84)
Weighted average number of common shares
Basic and diluted (in shares)	56,850,172	55,421,504	56,469,358	55,241,284

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) Condensed Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (82,503)	$ (24,473)	$ (129,069)	$ (38,811)
Other comprehensive income (loss):
Share of other comprehensive income (loss) of equity method investment (note 4)	27	(12)	(47)	(12)
Comprehensive loss	$ (82,476)	$ (24,485)	$ (129,116)	$ (38,823)

Condensed Consolidated Statem_3

Condensed Consolidated Statement of Stockholders' Equity - USD ($) $ in Thousands	Total	Convertible Preferred Shares	Common Shares	Additional Paid-In Capital	Deficit	Accumulated Other Comprehensive Loss
Beginning balance (in shares) at Dec. 31, 2017		500,000	55,060,650
Beginning balance at Dec. 31, 2017	$ 182,473	$ 49,780	$ 876,108	$ 42,840	$ (738,070)	$ (48,185)
Accretion of accumulated dividends on Preferred Shares	0	$ 2,336			(2,336)
Stock-based compensation	1,510			1,510
Certain fair value adjustments to liability-classified	(504)			(504)
Issuance of common shares pursuant to the Sale Agreement (shares)		664,000
Issuance of common shares pursuant to the Sale Agreement	66,265	$ 66,265
Issuance of common shares pursuant to exercise of options (in shares)			26,541
Issuance of common shares pursuant to exercise of options	103		$ 180	(77)
Net loss	(17,429)				(17,429)
Ending balance (in shares) at Mar. 31, 2018		1,164,000	55,087,191
Ending balance at Mar. 31, 2018	232,418	$ 118,381	$ 876,288	43,769	(757,835)	(48,185)
Beginning balance (in shares) at Dec. 31, 2017		500,000	55,060,650
Beginning balance at Dec. 31, 2017	182,473	$ 49,780	$ 876,108	42,840	(738,070)	(48,185)
Net loss	(38,811)
Ending balance (in shares) at Sep. 30, 2018		1,164,000	55,472,319
Ending balance at Sep. 30, 2018	215,272	$ 123,489	$ 878,805	45,500	(784,325)	(48,197)
Beginning balance (in shares) at Mar. 31, 2018		1,164,000	55,087,191
Beginning balance at Mar. 31, 2018	232,418	$ 118,381	$ 876,288	43,769	(757,835)	(48,185)
Accretion of accumulated dividends on Preferred Shares	0	$ 2,541			(2,541)
Stock-based compensation	1,862			1,862
Certain fair value adjustments to liability-classified	(34)			(34)
Issuance of common shares pursuant to exercise of options (in shares)			238,059
Issuance of common shares pursuant to exercise of options	735		$ 1,903	(1,168)
Net loss	3,091				3,091
Ending balance (in shares) at Jun. 30, 2018		1,164,000	55,325,250
Ending balance at Jun. 30, 2018	238,072	$ 120,922	$ 878,191	44,429	(757,285)	(48,185)
Accretion of accumulated dividends on Preferred Shares	0	$ 2,567			(2,567)
Stock-based compensation	1,658			1,658
Certain fair value adjustments to liability-classified	(407)			(407)
Issuance of common shares pursuant to exercise of options (in shares)			147,069
Issuance of common shares pursuant to exercise of options	434		$ 614	(180)
Currency translation adjustment	(12)					(12)
Net loss	(24,473)				(24,473)
Ending balance (in shares) at Sep. 30, 2018		1,164,000	55,472,319
Ending balance at Sep. 30, 2018	215,272	$ 123,489	$ 878,805	45,500	(784,325)	(48,197)
Beginning balance (in shares) at Dec. 31, 2018		1,164,000	55,518,800
Beginning balance at Dec. 31, 2018	200,234	$ 126,136	$ 879,405	48,084	(805,221)	(48,170)
Accretion of accumulated dividends on Preferred Shares		$ 2,715			(2,715)
Stock-based compensation	1,665			1,665
Certain fair value adjustments to liability-classified	47			47
Issuance of common shares pursuant to the Sale Agreement (shares)			614,401
Issuance of common shares pursuant to the Sale Agreement	2,248		$ 2,248
Issuance of common shares pursuant to exercise of options (in shares)			122,603
Issuance of common shares pursuant to exercise of options	288		$ 490	(202)
Currency translation adjustment	(22)					(22)
Net loss	(23,251)				(23,251)
Ending balance (in shares) at Mar. 31, 2019		1,164,000	56,255,804
Ending balance at Mar. 31, 2019	181,209	$ 128,851	$ 882,143	49,594	(831,187)	(48,192)
Beginning balance (in shares) at Dec. 31, 2018		1,164,000	55,518,800
Beginning balance at Dec. 31, 2018	200,234	$ 126,136	$ 879,405	48,084	(805,221)	(48,170)
Net loss	(129,069)
Ending balance (in shares) at Sep. 30, 2019		1,164,000	56,850,172
Ending balance at Sep. 30, 2019	83,637	$ 134,405	$ 884,623	55,385	(942,559)	(48,217)
Beginning balance (in shares) at Mar. 31, 2019		1,164,000	56,255,804
Beginning balance at Mar. 31, 2019	181,209	$ 128,851	$ 882,143	49,594	(831,187)	(48,192)
Accretion of accumulated dividends on Preferred Shares		$ 2,762			(2,762)
Stock-based compensation	3,915			3,915
Certain fair value adjustments to liability-classified	230			230
Issuance of common shares pursuant to the Sale Agreement (shares)			593,689
Issuance of common shares pursuant to the Sale Agreement	2,477		$ 2,477
Issuance of common shares pursuant to exercise of options (in shares)			679
Issuance of common shares pursuant to exercise of options	2		$ 3	(1)
Currency translation adjustment	(52)					(52)
Net loss	(23,315)				(23,315)
Ending balance (in shares) at Jun. 30, 2019		1,164,000	56,850,172
Ending balance at Jun. 30, 2019	164,466	$ 131,613	$ 884,623	53,738	(857,264)	(48,244)
Accretion of accumulated dividends on Preferred Shares		$ 2,792			(2,792)
Stock-based compensation	1,592			1,592
Certain fair value adjustments to liability-classified	55			55
Currency translation adjustment	27					27
Net loss	(82,503)				(82,503)
Ending balance (in shares) at Sep. 30, 2019		1,164,000	56,850,172
Ending balance at Sep. 30, 2019	$ 83,637	$ 134,405	$ 884,623	$ 55,385	$ (942,559)	$ (48,217)

Condensed Consolidated Statem_4

Condensed Consolidated Statement of Stockholders' Equity (Parenthetical) $ in Thousands	3 Months Ended
	Mar. 31, 2018USD ($)
Statement of Stockholders' Equity [Abstract]
Issuance costs on preferred stock issued	$ 135

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flow - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
OPERATING ACTIVITIES
Net loss	$ (82,503)	$ (24,473)	$ (129,069)	$ (38,811)
Items not involving cash:
Deferred income tax benefit	(12,661)	(4,282)	(12,661)	(4,282)
Depreciation	507	497	1,521	1,677
Loss (gain) on sale of property and equipment	0	(26)	(11)	(26)
Stock-based compensation expense	1,516	1,828	6,822	5,445
Unrealized foreign exchange losses (gains)	24	(131)	(71)	795
Change in fair value of contingent consideration	(376)	(5,608)	(121)	(6,263)
Impairment of intangible assets	43,836	14,811	43,836	14,811
Impairment of goodwill	22,471	0	22,471	0
Site consolidation non-cash portion	0	0	0	396
Gain on investment	0	0	0	(24,884)
Equity investment loss	3,512	2,838	11,497	2,838
Non-cash royalty revenue	(979)	0	(979)	0
Non-cash interest expense	1,106	0	1,106	0
Net change in non-cash operating items:
Accounts receivable	(957)	784	(1,057)	(136)
Prepaid expenses and other assets	1,080	109	1,839	1,017
Accrued revenue	0	0	0	128
Accounts payable and accrued liabilities	538	1,094	(1,320)	(2,171)
Deferred revenue	0	(325)	0	(2,093)
Restructuring accrual	(138)	(320)	(917)	770
Other liabilities	(446)	0	(541)	(2)
Net cash used in operating activities	(23,470)	(13,204)	(57,655)	(50,791)
INVESTING ACTIVITIES
Acquisition of short and long-term investments	0	0	0	(48,025)
Disposition of short and long-term investments	16,410	24,590	87,675	0
Proceeds from sale of property and equipment	0	25	11	25
Acquisition of property and equipment	(255)	(237)	(526)	(911)
Net cash provided by (used) in investing activities	16,155	24,378	87,160	(48,911)
FINANCING ACTIVITIES
Proceeds from sale of future royalties, net	18,549	0	18,549	0
Promissory note repayment	0	0	0	(12,001)
Proceeds from sale of Series A Preferred Shares, net of issuance costs	0	0	0	66,265
Issuance of common shares pursuant to the ATM	0	0	4,725	0
Issuance of common shares pursuant to exercise of options	0	435	290	1,273
Net cash provided by financing activities	18,549	435	23,564	55,537
Effect of foreign exchange rate changes on cash and cash equivalents	(24)	131	71	(795)
Increase in cash and cash equivalents	11,210	11,740	53,140	(44,960)
Cash and cash equivalents, beginning of period	78,872	10,193	36,942	66,893
Cash and cash equivalents, end of period	90,082	21,933	90,082	21,933
Non-cash transactions:
Preferred shares dividends accrued	(2,792)	(2,567)	(8,269)	(7,444)
Investment in Genevant	$ 0	$ 0	$ 0	$ 24,665

Nature of Business and Future O

Nature of Business and Future Operations	9 Months Ended
	Sep. 30, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Nature of business and future operations	Nature of business and future operations Arbutus Biopharma Corporation (the “Company” or “Arbutus”) is a biopharmaceutical business dedicated to discovering, developing, and commercializing a cure for patients suffering from chronic hepatitis B infection, a disease of the liver caused by the hepatitis B virus (“HBV”). To pursue its strategy of developing a curative combination regimen, the Company has assembled a pipeline of multiple drug candidates with differing and complementary mechanisms of action targeting HBV. These include AB-729, the Company's subcutaneously-delivered RNA interference ("RNAi") therapeutic candidate currently in a Phase 1a/1b clinical trial, AB-452, the Company's lead oral HBV RNA destabilizer candidate currently in pre-clinical testing, next-generation oral capsid inhibitor compounds, and compounds that inhibit PD-L1. The success of the Company is dependent on obtaining the necessary regulatory approvals to bring its products to market and achieving profitable operations. The Company's research and development activities and commercialization of its products are dependent on its ability to successfully complete these activities and to obtain adequate financing through a combination of financing activities and operations. It is not possible to predict either the outcome of the Company's existing or future research and development programs or the Company’s ability to continue to fund these programs in the future.

Significant Accounting Policies

Significant Accounting Policies	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Significant accounting policies	Significant accounting policies Basis of presentation These unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial statements and accordingly, do not include all disclosures required for annual financial statements. These statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto for the year ended December 31, 2018 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (the “2018 Form 10-K”). These unaudited condensed consolidated financial statements reflect, in the opinion of management, all adjustments and reclassifications necessary to fairly present the Company's financial position as of September 30, 2019 and the Company's results of operations and cash flows for the three and nine months ended September 30, 2019 and 2018 . The results of operations for the three and nine months ended September 30, 2019 and 2018 , respectively, are not necessarily indicative of the results for the full year. These unaudited condensed consolidated financial statements follow the same significant accounting policies as those described in the notes to the audited consolidated financial statements of the Company for the year ended December 31, 2018 , except as described below under Recent Accounting Pronouncements. Principles of consolidation These unaudited condensed consolidated financial statements include the accounts of the Company and its two wholly-owned subsidiaries, Arbutus Biopharma Inc. ("Arbutus Inc.") and Arbutus Biopharma US Holdings, Inc. All intercompany transactions and balances have been eliminated in consolidation. Income or loss per share The Company follows the two-class method when computing net loss attributable to common shareholders per share as the Company has issued Series A participating convertible preferred shares (the "Preferred Shares"), as further described in note 12, that meet the definition of participating securities. The Preferred Shares entitle the holders to participate in dividends but do not require the holders to participate in losses of the Company. Accordingly, if the Company reports a net loss attributable to holders of the Company's common shares, net losses are not allocated to holders of the Preferred Shares. Net loss attributable to common shareholders per share is calculated based on the weighted average number of common shares outstanding. The calculation of diluted net loss attributable to common shareholders per share does not differ from the calculation of basic net loss attributable to common shareholders per share, as the effect of the Company’s dilutive potential common shares was anti-dilutive. During the nine months ended September 30, 2019 and 2018 , potential common shares of approximately 28.2 million and 24.2 million , respectively, consisting of the "if-converted" number of Preferred Shares and outstanding stock options, were excluded from the calculation of net loss per common share because their inclusion would be anti-dilutive. The following table sets out the computation of basic and diluted net loss attributable to common shareholders per share: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands, except share and per share amounts) Numerator: Allocation of distributable earnings $ — $ — $ — $ — Allocation of undistributable loss (85,295 ) (27,040 ) (137,338 ) (46,255 ) Allocation of loss attributed to common shareholders $ (85,295 ) $ (27,040 ) $ (137,338 ) $ (46,255 ) Denominator: Weighted average number of common shares - basic and diluted 56,850,172 55,421,504 56,469,358 55,241,284 Basic and diluted net loss attributable to common shareholders per share $ (1.50 ) $ (0.49 ) $ (2.43 ) $ (0.84 ) Equity method investment The Company accounts for its investment in associated companies in accordance with the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") 323, Investments - Equity Method and Joint Ventures ("ASC 323"). In accordance with ASC 323, associated companies are accounted for as equity method investments. Results of associated companies are presented on a one-line basis. Investments in, and advances to, associated companies are presented on a one-line basis in the caption “Investment in Genevant” in the Company's Condensed Consolidated Balance Sheets, net of allowance for losses, which represents the Company's best estimate of probable losses inherent in such assets. The Company's proportionate share of any associated companies' net income or loss is presented on a one-line basis in the caption "Equity investment (loss)" in the Company's Condensed Consolidated Statement of Operations. Transactions between the Company and any associated companies are eliminated on a basis proportional to the Company's ownership interest. Financial results of Genevant Sciences Ltd. ("Genevant") are recorded on a one-quarter lag basis. Revenue recognition The Company recognizes the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers under a five-step model: (i) identify contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when or as a performance obligation is satisfied. The Company generates revenue primarily through collaboration agreements and license agreements. Such agreements may require the Company to deliver various rights and/or services, including intellectual property rights or licenses and research and development services. Under such agreements, the Company is generally eligible to receive non-refundable upfront payments, funding for research and development services, milestone payments, and royalties. In contracts where the Company has more than one performance obligation to provide its customer with goods or services, each performance obligation is evaluated to determine whether it is distinct based on whether (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available and (ii) the good or service is separately identifiable from other promises in the contract. The consideration under the contract is then allocated between the distinct performance obligations based on their respective relative stand-alone selling prices. The estimated stand-alone selling price of each deliverable reflects the Company's best estimate of what the selling price would be if the deliverable was regularly sold on a stand-alone basis and is determined by reference to market rates for the good or service when sold to others or by using an adjusted market assessment approach if the selling price on a stand-alone basis is not available. The consideration allocated to each distinct performance obligation is recognized as revenue when control is transferred to the customer for the related goods or services. Consideration associated with at-risk substantive performance milestones, including sales-based milestones, is recognized as revenue when it is probable that a significant reversal of the cumulative revenue recognized will not occur. Sales-based royalties received in connection with licenses of intellectual property are subject to a specific exception in the revenue standards, whereby the consideration is not included in the transaction price and recognized in revenue until the customer’s subsequent sales or usages occur. Segment information The Company operates as a single segment. Recent accounting pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on the Company's financial position or results of operations upon adoption. The Company adopted Accounting Standard Update (“ASU”) No. 2016-02, Leases (Topic 842), as of January 1, 2019, using the modified retrospective approach with the effective date transition method (note 5). Accordingly, all periods prior to adoption are presented in accordance with legacy accounting and the Company recorded no retrospective adjustments to the comparative periods presented. In addition, the Company elected the package of practical expedients permitted under the transition guidance within ASC 842, which among other things, allowed the Company to carry forward its historical lease classification. In addition, the Company elected the short term exemption, which allows entities to not capitalize their leases with a term of 12 months or less. Adoption of the new standard resulted in the recording of operating lease right-of-use assets (“ROU assets”) and lease liabilities of approximately $3.2 million and $4.1 million , respectively, as of January 1, 2019. The standard did not materially impact the Company’s consolidated statements of operations and statements of cash flow. In November 2018, the FASB issued targeted amendments to ASU No. 2018-18, Collaborative Arrangements (Topic 808), and ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606), to clarify that certain transactions between parties to collaborative arrangements should be accounted for in accordance with FASB revenue guidance when the counterparty is a customer. This guidance also prohibits the presentation of collaborative arrangements as revenues from contracts with customers if the counterparty is not a customer. This guidance, which is required to be applied retrospectively and is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted, is not expected to have a material impact on the Company’s consolidated financial statements.

Fair Value of Financial Instrum

Fair Value of Financial Instruments	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Fair value of financial instruments	Fair value of financial instruments The Company measures certain financial instruments and other items at fair value. To determine the fair value, the Company uses the fair value hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use to value an asset or liability and are developed based on market data obtained from independent sources. Unobservable inputs are inputs based on assumptions about the factors market participants would use to value an asset or liability. The three levels of inputs that may be used to measure fair value are as follows: • Level 1 inputs are quoted market prices for identical instruments available in active markets. • Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability either directly or indirectly. If the asset or liability has a contractual term, the input must be observable for substantially the full term. An example includes quoted market prices for similar assets or liabilities in active markets. • Level 3 inputs are unobservable inputs for the asset or liability and will reflect management’s assumptions about market assumptions that would be used to price the asset or liability. The following table presents information about the Company’s assets and liabilities that are measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation techniques used to determine such fair value: Level 1 Level 2 Level 3 Total As of September 30, 2019 (in thousands) Assets Cash and cash equivalents $ 90,082 $ — $ — $ 90,082 Liabilities Liability-classified options — — 86 86 Contingent consideration — — 3,005 3,005 Total $ — $ — $ 3,091 $ 3,091 Level 1 Level 2 Level 3 Total As of December 31, 2018 (in thousands) Assets Cash and cash equivalents $ 36,942 $ — $ — $ 36,942 Short-term investments 87,675 — — 87,675 Total 124,617 — — 124,617 Liabilities Liability-classified stock option awards — — 479 479 Contingent consideration — — 3,126 3,126 Total $ — $ — $ 3,605 $ 3,605 The Company's liability-classified options are measured at fair value using the Black-Scholes valuation model. Assumptions about the Company's expected stock-price volatility are based on the historical volatility of the Company's publicly-traded stock. The risk-free interest rate used for each grant is equal to the zero coupon rate for instruments with a similar expected life. The assumptions around the expected life are based on the Company's historical data. To determine the fair value of the contingent consideration, the Company uses a probability-weighted assessment of the likelihood the milestones would be met and the estimated timing of such payments (see note 10). The potential contingent payments are then discounted to their present value using a probability-adjusted discount rate that reflects the early-stage nature of the development program, time to complete the program development, and overall biotech indices. The following table presents the changes in fair value of the Company’s liability-classified stock option awards: Liability at beginning of the period Fair value of liability-classified options exercised in the period Increase (decrease) in fair value of liability Liability at end of the period (in thousands) Nine months ended September 30, 2018 $ 1,239 $ — $ 1,499 $ 2,738 Nine months ended September 30, 2019 $ 479 $ — $ (393 ) $ 86 The following table presents the changes in fair value of the Company’s contingent consideration: Liability at beginning of the period Increase (decrease) in fair value of liability Liability at end of the period (in thousands) Nine months ended September 30, 2018 $ 10,424 $ (6,263 ) $ 4,161 Nine months ended September 30, 2019 $ 3,126 $ (121 ) $ 3,005

Equity Method Investment

Equity Method Investment	9 Months Ended
	Sep. 30, 2019
Equity Method Investments and Joint Ventures [Abstract]
Equity method investment	Equity method investment In April 2018, the Company entered into an agreement with Roivant Sciences Ltd. (“Roivant”), its largest shareholder, to launch Genevant, a company focused on the discovery, development, and commercialization of a broad range of RNA-based therapeutics enabled by the Company's lipid nanoparticle ("LNP") and ligand conjugate delivery technologies. The Company licensed exclusive rights to its LNP and ligand conjugate delivery platforms to Genevant for RNA-based applications outside of HBV. Genevant plans to develop products in-house and pursue industry partnerships to build a diverse pipeline of therapeutics across multiple modalities, including RNAi, mRNA, and gene editing. Under the terms of the agreement, Roivant contributed $ 37.5 million in seed capital to Genevant. The Company retained all rights to its LNP and conjugate delivery platforms for HBV, and is entitled to a tiered low single-digit royalty from Genevant on future sales of products enabled by the delivery platforms licensed to Genevant. The Company also retained the entirety of its royalty entitlement on the commercialization of Alnylam Pharmaceuticals Inc.'s ("Alnylam") ONPATTRO™ (Patisiran/ALN-TTR02). The Company recognized a non-cash gain of $24.9 million in the second quarter of 2018 in connection with the equity interest received by Arbutus upon Genevant’s formation. As of September 30, 2019 , the Company held an equity interest of approximately 40% of the common equity of Genevant and accounts for its interest in Genevant using the equity method. The carrying value of the Company's interest in Genevant as of September 30, 2019 was $11.0 million . The basis difference between the Company’s carrying value in Genevant and the Company’s share of Genevant's net assets is attributed primarily to indefinite-lived in-process research and development ("IPR&D") (the delivery technology transferred to Genevant). For the three and nine months ended September 30, 2019 , the Company recorded equity investment losses of $3.5 million and $11.5 million , respectively, for its proportionate share of Genevant’s net loss, recorded on a one-quarter lag basis.

Leases

Leases	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Leases	Leases The Company has two operating leases for office and laboratory space. The Company's corporate headquarters is located at 701 Veterans Circle, Warminster, Pennsylvania. The lease expires on April 30, 2027, and the Company has the option of extending the lease for two further five -year terms. The Company also leases office space located at 626 Jacksonville Rd, Warminster, Pennsylvania under a lease that expires on December 31, 2021, and the Company has an option to extend the lease term to April 30, 2027. In connection with the Company's site consolidation in 2018, the Company ceased using its office and laboratory space located in Burnaby, British Columbia, Canada on June 30, 2018. The Company subleased a portion of the Burnaby facility to various tenants, including Genevant, until the lease expired on July 31, 2019. The Company recognized the remaining lease payments for the Burnaby facility, less sublease income under contract, in site consolidation expenses in 2018. The Company’s lease agreements do not contain any material residual value guarantees or material restrictive covenants. The Company adopted ASU No. 2016-02, Leases (Topic 842) on January 1, 2019 using the modified retrospective basis applied at the effective date of the new standard and elected to utilize a package of practical expedients. Leases with an initial term of 12 months or less are not recorded on the balance sheet. The Company determines if an arrangement is a lease at inception. Right-of-use assets represent the Company's right to use an underlying asset for the lease term and lease liabilities represent the Company's obligation to make lease payments arising from the lease. Operating lease right-of-use assets and lease liabilities are recognized based on the present value of lease payments over the lease term. The leases do not provide an implicit rate so, in determining the present value of lease payments, the Company utilized its incremental borrowing rate for the applicable lease, which was 9.0% for the 701 Veterans Circle lease, 7.6% for the 626 Jacksonville Rd. lease and 5.0% for the Burnaby lease. The Company recognizes lease expense on a straight-line basis over the remaining lease term. During the nine months ended September 30, 2019 , the Company incurred total operating lease expenses of $1.1 million , which included lease expenses associated with fixed lease payments of $0.9 million , and variable payments associated with common area maintenance and similar expenses of $0.2 million . For the nine months ended September 30, 2018 , the straight-line fixed expense for leases was $0.9 million . Sublease income for the nine months ended September 30, 2019 was $0.2 million , versus $0.1 million for the nine months ended September 30, 2018 . Weighted average remaining lease term and discount rate were as follows: As of September 30, 2019 Weighted-average remaining lease term (years) 7.3 Weighted average discount rate 8.9% The Company did not include options to extend its lease terms as part of its ROU asset and lease liabilities. Supplemental cash flow information related to the Company's operating leases was as follows: Nine Months Ended September 30, 2019 2018 (in thousands) Cash paid for amounts included in the measurement of lease liabilities $ 921 $ — Maturities of lease liabilities were as follows: As of September 30, 2019 (in thousands) October through December 2019 $ 188 2020 657 2021 677 2022 581 2023 598 Thereafter 2,039 Total Lease Payments $ 4,740 Less: interest (1,268 ) Present value of lease payments $ 3,472

Intangible Assets and Goodwill

Intangible Assets and Goodwill	9 Months Ended
	Sep. 30, 2019
Goodwill and Intangible Assets Disclosure [Abstract]
Intangible assets and goodwill	Intangible assets and goodwill Acquired IPR&D intangible assets relate to the Company's covalently closed circular DNA ("cccDNA") program. During the three months ended September 30, 2019 , the Company recorded a $43.8 million non-cash impairment expense to reduce the carrying value of its IPR&D intangible assets to zero as of September 30, 2019. The Company also recognized a corresponding income tax benefit of $12.7 million related to the decrease in its deferred tax liability related to the IPR&D intangible assets. The impairment was due to a decision to delay indefinitely the further development of the Company's cccDNA program while the Company focuses on its other development programs. Goodwill represents the excess of purchase price over the value assigned to the net tangible and identifiable intangible assets in connection with the business combination that formed Arbutus. In the third quarter of 2019, the Company assessed the changes in circumstances that occurred during the quarter to determine if it was more likely than not that the fair value of its single reporting unit was below its carrying amount. Although the Company's annual impairment test is performed during the fourth quarter, the Company performs this qualitative assessment each interim reporting period. Due to a sustained decrease in the Company's share price in recent months, the Company's market capitalization was reduced below the book value of its net assets and the Company concluded that the fair value of its single reporting unit was below its carrying amount by an amount in excess of the carrying value of the goodwill. As a result, the Company recorded a $22.5 million non-cash impairment expense to reduce the carrying value of its goodwill asset to zero as of September 30, 2019.

Accounts Payable and Accrued Li

Accounts Payable and Accrued Liabilities	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Accounts payable and accrued liabilities	Accounts payable and accrued liabilities Accounts payable and accrued liabilities are comprised of the following: September 30, 2019 December 31, 2018 (in thousands) Trade accounts payable $ 1,400 $ 3,192 Research and development accruals 4,112 2,716 Professional fee accruals 1,177 871 Payroll accruals 1,509 2,341 Other accrued liabilities 1 309 $ 8,199 $ 9,429

Site Consolidation

Site Consolidation	9 Months Ended
	Sep. 30, 2019
Restructuring and Related Activities [Abstract]
Site consolidation	Site consolidation In 2018, the Company substantially completed a site consolidation and organizational restructuring to align its HBV business in Warminster, PA, including a reduction of its global workforce and closure of its Burnaby facility. The Company estimates that the total expenses to complete the site consolidation will be approximately $5.0 million, of which $4.8 million has been incurred as of September 30, 2019 . Included in the site consolidation plan was the payment of one-time employee termination benefits, employee relocation costs, and site closure costs. The Company ceased using its Burnaby facility as of June 30, 2018 and recognized the remaining committed cost, less sublease income under contract, in site consolidation expenses in 2018. The lease for the Burnaby facility expired on July 31, 2019. Site consolidation expenses were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands) Employee severance and relocation $ 231 $ 198 $ 429 $ 3,399 Facility and other expenses (49 ) (690 ) (396 ) 311 Total site consolidation expense $ 182 $ (492 ) $ 33 $ 3,710 Site consolidation activity was as follows: Employee severance and relocation Facility and other expenses Total (in thousands) Site consolidation accrual as of December 31, 2018 $ 697 $ 634 $ 1,331 Additional accruals and other adjustments 429 (396 ) 33 Payments (923 ) (238 ) (1,161 ) Site consolidation accrual as of September 30, 2019 $ 203 $ — $ 203

Sale of Future Royalties

Sale of Future Royalties	9 Months Ended
	Sep. 30, 2019
Other Liabilities Disclosure [Abstract]
Sale of future royalties	Sale of future royalties On July 2, 2019, the Company entered into a Purchase and Sale Agreement (the "Agreement") with the Ontario Municipal Employees Retirement System (or "OMERS"), pursuant to which the Company sold to OMERS part of its royalty interest on future global net sales of ONPATTRO™ (Patisiran) ("ONPATTRO"), an RNA interference therapeutic currently being sold by Alnylam. ONPATTRO utilizes Arbutus’ LNP technology, which was licensed to Alnylam pursuant to the Cross-License Agreement, dated November 12, 2012, by and between the Company and Alnylam (the “LNP License Agreement”). Under the terms of the LNP License Agreement, the Company is entitled to tiered royalty payments on global net sales of ONPATTRO ranging from 1.00% to 2.33% after offsets, with the highest tier applicable to annual net sales above $500 million . This royalty interest was sold to OMERS, effective as of January 1, 2019, for $20 million in gross proceeds before advisory fees. OMERS will retain this entitlement until it has received $30 million in royalties, at which point 100% of such royalty interest on future global net sales of ONPATTRO will revert to the Company. OMERS has assumed the risk of collecting up to $30 million of future royalty payments from Alnylam and Arbutus is not obligated to reimburse OMERS if they fail to collect any such future royalties. The $30 million in royalties to be paid to OMERS is accounted for as a liability, with the difference between the liability and the gross proceeds received accounted for as a discount. The discount, as well as $1.5 million of transaction costs, will be amortized as interest expense based on the projected balance of the liability as of the beginning of each period. Management estimated an effective annual interest rate of approximately 25% . Over the course of the Agreement, the actual interest rate will be affected by the amount and timing of royalty revenue recognized and changes in the timing of forecasted royalty revenue. On a quarterly basis, the Company will reassess the expected timing of the royalty revenue, recalculate the amortization and effective interest rate and adjust the accounting prospectively as needed. The Company will recognize non-cash royalty revenue related to the sales of ONPATTRO during the term of the Agreement. As royalties are remitted to OMERS from Alnylam, the balance of the recognized liability will be effectively repaid over the life of the Agreement. There are a number of factors that could materially affect the amount and timing of royalty payments from Alnylam, none of which are within the Company's control. During the three and nine months ended September 30, 2019 , the Company recognized non-cash royalty revenue of $1.0 million and $1.1 million of related non-cash interest expense. The table below shows the activity related to the net liability from inception of the Agreement through September 30, 2019 : Nine Months Ended September 30, 2019 (in thousands) Net liability related to sale of future royalties - beginning balance $ — Initial recognition of liability 30,000 Debt discount and issuance costs (11,451 ) Non-cash royalty revenue (979 ) Non-cash interest expense 1,106 Net liability related to sale of future royalties - ending balance $ 18,675 In addition to the royalty from the Alnylam LNP License Agreement, the Company is also receiving a second, lower royalty interest on global net sales of ONPATTRO originating from a settlement agreement and subsequent license agreement with Acuitas Therapeutics, Inc. ("Acuitas"). The royalty from Acuitas has been retained by the Company and was not part of the royalty sale to OMERS.

Contingencies and Commitments

Contingencies and Commitments	9 Months Ended
	Sep. 30, 2019
Commitments and Contingencies Disclosure [Abstract]
Contingencies and commitments	Contingencies and commitments Arbitration with the University of British Columbia Certain early work on LNP delivery systems and related inventions was undertaken by the Company and assigned to the University of British Columbia ("UBC"). These inventions were subsequently licensed back to the Company by UBC under a license agreement, initially entered into in 1998 and subsequently amended in 2001, 2006 and 2007. The Company has granted sublicenses under the UBC license to Alnylam. Alnylam has in turn sublicensed back to the Company under the licensed UBC patents for discovery, development and commercialization of siRNA products. Certain sublicenses were also granted to other parties. On November 10, 2014, UBC filed a notice of arbitration against the Company and on January 16, 2015, filed a Statement of Claim, which alleged entitlement to $3.5 million in allegedly unpaid royalties based on publicly available information, and an unspecified amount based on non-public information. UBC also sought interest and costs, including legal fees. The Company filed its Statement of Defense to UBC's Statement of Claims, as well as a Counterclaim involving a patent application that the Company alleged UBC wrongly licensed to a third party. The proceedings were divided into three phases, with the first hearing taking place in June 2017. In the first phase, the arbitrator determined which agreements are sublicense agreements within UBC's claim. Also in the first phase, UBC updated its alleged entitlement from $3.5 million originally claimed to seek $10.9 million in alleged unpaid royalties, plus interest arising from payments as early as 2008. The arbitrator also held in the first phase of the arbitration that the patent application that is the subject of the Counterclaim was not required to be licensed to Arbutus. The second phase of arbitration took place in April 2019. On August 20, 2019, the arbitrator issued his decision for the second phase of the arbitration, awarding UBC $5.9 million , which includes interest of approximately $2.6 million . The Company paid the $5.9 million award to UBC in September 2019. The arbitrator also held that the third phase of the arbitration, which would address patent validity, should the Company choose to pursue a third phase, would not provide a defense to the award. An award for costs and attorneys’ fees is still to be determined. The Company recorded a charge of $6.5 million in the third quarter of 2019, consisting of $5.9 million for the award (including interest) and $0.6 million for an estimate of a potential award for costs and attorney's fees. License Agreements between Enantigen and Blumberg and Drexel In October 2014, Arbutus Inc. acquired all of the outstanding shares of Enantigen Therapeutics, Inc. (“Enantigen”) pursuant to a stock purchase agreement. Through this transaction, Arbutus Inc. acquired a HBV surface antigen secretion inhibitor program and a capsid assembly inhibitor program. Under the stock purchase agreement, Arbutus Inc. agreed to pay up to a total of $21.0 million to Enantigen’s selling shareholders upon the achievement of specified development and regulatory milestones for (a) the first two products that contain either a capsid compound or an HBV surface antigen compound that is covered by a patent acquired under this agreement, or (b) a capsid compound from an agreed upon list of compounds. The amount paid could be up to an additional $102.5 million in sales performance milestones in connection with the sale of the first commercialized product by Arbutus Inc. for the treatment of HBV, regardless of whether such product is based upon assets acquired under this agreement, and a low single-digit royalty on net sales of such first commercialized HBV product, up to a maximum royalty payment of $1.0 million that, if paid, would be offset against Arbutus Inc.'s milestone payment obligations. The contingent consideration for this acquisition is a financial liability and measured at its fair value at each reporting period, with any changes in fair value from the previous reporting period recorded in the statement of operations and comprehensive loss (see note 3). The fair value of the contingent consideration was $3.0 million as of September 30, 2019 . Under the stock purchase agreement, Enantigen must also fulfill its obligations as they relate to the three patent license agreements with The Baruch S. Blumberg Institute ("Blumberg") and Drexel University ("Drexel"). Pursuant to each patent license agreement, Enantigen is obligated to pay Blumberg and Drexel up to approximately $0.5 million in development and regulatory milestones per licensed product, royalties in the low single-digits, and a percentage of revenue it receives from its sub-licensees. Research Collaboration and Funding Agreement with Blumberg In November 2018, the Company entered into a new two -year master services agreement with Blumberg that expires in November 2020. The new agreement replaces all rights and obligations of the prior research collaboration and funding agreements, as amended. Under the new agreement, Blumberg will perform specific research activities based upon statements of work and the Company will no longer provide a fixed amount of funding to Blumberg. As of September 30, 2019, the Company has executed statements of work with Blumberg for an aggregate cost of $0.8 million under this new agreement. Intellectual property that is generated during the research activities is the Company's exclusive property and all financial obligations for it to utilize the intellectual property are satisfied in the upfront cost of the research activities. Under the terms of the new agreement, the Company retains all rights to any inventions arising from performance of the agreement and no license is granted to Blumberg, nor are milestones for said inventions due to Blumberg.

Collaborations, Contracts and L

Collaborations, Contracts and Licensing Agreements	9 Months Ended
	Sep. 30, 2019
Revenue from Contract with Customer [Abstract]
Collaborations, contracts and licensing agreements	Collaborations, contracts and licensing agreements Revenue contracts are described in detail in the Overview section of Part I, Item 2, "Management's Discussion and Analysis of Financial Condition and Results of Operations" in the Company's 2018 Form 10-K. In 2012, the Company entered into a license agreement with Alnylam that entitles Alnylam to develop and commercialize products with the Company's LNP technology. Alnylam's ONPATTRO program, which represents the first approved application of LNP technology, was approved by the U.S. Food and Drug Administration ("FDA") and the European Medicines Agency ("EMA") during the third quarter of 2018 and was launched immediately upon approval in the US. The Company is entitled to tiered low to mid single-digit royalty payments on global net sales of ONPATTRO and received its first royalty payment in the fourth quarter of 2018. In July 2019, the Company sold a portion of its royalty entitlement for Alnylam's ONPATTRO to OMERS. See note 9 - Sale of future royalties for further details. Revenue for the three and nine months ended September 30, 2019 consists primarily of a net $1.5 million development milestone earned under our license agreement with Gritstone, royalties on net global sales of Alnylam's ONPATTRO, a milestone and royalties on net sales of Spectrum Pharmaceuticals, Inc.'s ("Spectrum") Marqibo ® and services provided to Gritstone Oncology, Inc. ("Gritstone"). Revenue for the three and nine months ended September 30, 2018 consisted primarily of revenue earned under our license agreement with Gritstone, including a net $1.3 million development milestone payment, the earned portion of an upfront license fee and services provided to Gritstone.

Stockholders' Equity and Stock-

Stockholders' Equity and Stock-based Compensation	9 Months Ended
	Sep. 30, 2019
Stockholders' Equity Note [Abstract]
Stockholders' equity and stock-based compensation	Stockholders' equity and stock-based compensation Open Market Sale Agreement In December 2018, the Company entered into an Open Market Sale Agreement (“Sale Agreement”) with Jefferies LLC, under which it may issue and sell common shares, from time to time, for an aggregate sales price of up to $50.0 million . For the nine months ended September 30, 2019 , the Company issued 1,208,090 common shares pursuant to the Sale Agreement, resulting in gross proceeds of approximately $5.2 million . There were no shares issued during the three months ended September 30, 2019 under the Sale Agreement. Series A participating convertible preferred shares In October 2017, the Company entered into a subscription agreement with Roivant for the sale of 1,164,000 Preferred Shares for gross proceeds of $116.4 million. These Preferred Shares are non-voting and accrue an 8.75% per annum coupon in the form of additional Preferred Shares, compounded annually, until October 16, 2021, at which time all the Preferred Shares will be subject to mandatory conversion into common shares (subject to limited exceptions in the event of certain fundamental corporate transactions relating to Arbutus’ capital structure or assets, which would permit earlier conversion at Roivant’s option). The conversion price is $7.13 per share, which will result in the Preferred Shares being converted into approximately 23 million common shares. After conversion of the Preferred Shares into common shares, based on the number of common shares outstanding as of September 30, 2019 , Roivant would hold approximately 49% of the Company's common shares. Roivant agreed to a four year lock-up period for this investment and its existing holdings in the Company. Roivant also agreed to a four year standstill whereby Roivant will not acquire greater than 49.99% of the Company's common shares or securities convertible into common shares. The initial investment of $50.0 million closed in October 2017, and the remaining amount of $66.4 million closed in January 2018 following regulatory and shareholder approvals. The Company records the Preferred Shares wholly as equity under ASC 480, Distinguishing Liabilities From Equity, with no bifurcation of conversion feature from the host contract, given that the Preferred Shares cannot be cash settled and the redemption features are within the Company's control, which include a fixed conversion ratio with predetermined timing and proceeds. The Company accrues for the 8.75% per annum compounding coupon at each reporting period end date as an increase to preferred share capital, and an increase to deficit (see Condensed Consolidated Statement of Stockholders' Equity).

Related Party Transaction

Related Party Transaction	9 Months Ended
	Sep. 30, 2019
Related Party Transactions [Abstract]
Related party transactions	Related Party Transactions Through the first quarter of 2019, the Company purchased certain research and development services from Genevant. These services were billed at agreed hourly rates and were reflective of market rates for such services. The total cost of these services for the nine months ended September 30, 2019 was $33 thousand . There were no such costs incurred during the second and third quarter of 2019. The total cost of these services was $0.1 million and $0.2 million for the three and nine months ended September 30, 2018 , respectively, and are included in the Condensed Consolidated Statements of Operations under research and development. Conversely, Genevant purchased certain administrative and transitional services from the Company totaling $40 thousand and $284 thousand for the three and nine months ended September 30, 2019 , respectively. The total income from these services was $0.1 million and $0.3 million for the three and nine months ended September 30, 2018 , which were netted against research and development expenses in the Condensed Consolidated Statements of Operations. In addition, Genevant had a sublease for 17,900 square feet in the Company's Burnaby facility. Sublease income from Genevant was $21 thousand and $0.1 million for the three and nine months ended September 30, 2019 , respectively, and was netted against site consolidation costs and lease liability (see notes 7 and 8). The Company’s Burnaby facility lease and the corresponding sublease to Genevant expired on July 31, 2019.

Significant Accounting Polici_2

Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Basis of presentation	Basis of presentation These unaudited condensed consolidated financial statements have been prepared in accordance with U.S. generally accepted accounting principles (“U.S. GAAP”) for interim financial statements and accordingly, do not include all disclosures required for annual financial statements. These statements should be read in conjunction with the Company’s audited consolidated financial statements and notes thereto for the year ended December 31, 2018 included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2018 (the “2018 Form 10-K”). These unaudited condensed consolidated financial statements reflect, in the opinion of management, all adjustments and reclassifications necessary to fairly present the Company's financial position as of September 30, 2019 and the Company's results of operations and cash flows for the three and nine months ended September 30, 2019 and 2018 . The results of operations for the three and nine months ended September 30, 2019 and 2018 , respectively, are not necessarily indicative of the results for the full year. These unaudited condensed consolidated financial statements follow the same significant accounting policies as those described in the notes to the audited consolidated financial statements of the Company for the year ended December 31, 2018 , except as described below under Recent Accounting Pronouncements.
Principles of consolidation	Principles of consolidation These unaudited condensed consolidated financial statements include the accounts of the Company and its two wholly-owned subsidiaries, Arbutus Biopharma Inc. ("Arbutus Inc.") and Arbutus Biopharma US Holdings, Inc. All intercompany transactions and balances have been eliminated in consolidation.
Income or loss per share	Income or loss per share The Company follows the two-class method when computing net loss attributable to common shareholders per share as the Company has issued Series A participating convertible preferred shares (the "Preferred Shares"), as further described in note 12, that meet the definition of participating securities. The Preferred Shares entitle the holders to participate in dividends but do not require the holders to participate in losses of the Company. Accordingly, if the Company reports a net loss attributable to holders of the Company's common shares, net losses are not allocated to holders of the Preferred Shares. Net loss attributable to common shareholders per share is calculated based on the weighted average number of common shares outstanding. The calculation of diluted net loss attributable to common shareholders per share does not differ from the calculation of basic net loss attributable to common shareholders per share, as the effect of the Company’s dilutive potential common shares was anti-dilutive. During the nine months ended September 30, 2019 and 2018 , potential common shares of approximately 28.2 million and 24.2 million , respectively, consisting of the "if-converted" number of Preferred Shares and outstanding stock options, were excluded from the calculation of net loss per common share because their inclusion would be anti-dilutive.
Equity method investment	Equity method investment The Company accounts for its investment in associated companies in accordance with the Financial Accounting Standards Board ("FASB") Accounting Standards Codification ("ASC") 323, Investments - Equity Method and Joint Ventures ("ASC 323"). In accordance with ASC 323, associated companies are accounted for as equity method investments. Results of associated companies are presented on a one-line basis. Investments in, and advances to, associated companies are presented on a one-line basis in the caption “Investment in Genevant” in the Company's Condensed Consolidated Balance Sheets, net of allowance for losses, which represents the Company's best estimate of probable losses inherent in such assets. The Company's proportionate share of any associated companies' net income or loss is presented on a one-line basis in the caption "Equity investment (loss)" in the Company's Condensed Consolidated Statement of Operations. Transactions between the Company and any associated companies are eliminated on a basis proportional to the Company's ownership interest. Financial results of Genevant Sciences Ltd. ("Genevant") are recorded on a one-quarter lag basis.
Revenue recognition	Revenue recognition The Company recognizes the amount of revenue to which it expects to be entitled for the transfer of promised goods or services to customers under a five-step model: (i) identify contract(s) with a customer; (ii) identify the performance obligations in the contract; (iii) determine the transaction price; (iv) allocate the transaction price to the performance obligations in the contract; and (v) recognize revenue when or as a performance obligation is satisfied. The Company generates revenue primarily through collaboration agreements and license agreements. Such agreements may require the Company to deliver various rights and/or services, including intellectual property rights or licenses and research and development services. Under such agreements, the Company is generally eligible to receive non-refundable upfront payments, funding for research and development services, milestone payments, and royalties. In contracts where the Company has more than one performance obligation to provide its customer with goods or services, each performance obligation is evaluated to determine whether it is distinct based on whether (i) the customer can benefit from the good or service either on its own or together with other resources that are readily available and (ii) the good or service is separately identifiable from other promises in the contract. The consideration under the contract is then allocated between the distinct performance obligations based on their respective relative stand-alone selling prices. The estimated stand-alone selling price of each deliverable reflects the Company's best estimate of what the selling price would be if the deliverable was regularly sold on a stand-alone basis and is determined by reference to market rates for the good or service when sold to others or by using an adjusted market assessment approach if the selling price on a stand-alone basis is not available. The consideration allocated to each distinct performance obligation is recognized as revenue when control is transferred to the customer for the related goods or services. Consideration associated with at-risk substantive performance milestones, including sales-based milestones, is recognized as revenue when it is probable that a significant reversal of the cumulative revenue recognized will not occur. Sales-based royalties received in connection with licenses of intellectual property are subject to a specific exception in the revenue standards, whereby the consideration is not included in the transaction price and recognized in revenue until the customer’s subsequent sales or usages occur.
Segment information	Segment information The Company operates as a single segment.
Recent accounting pronouncements	Recent accounting pronouncements From time to time, new accounting pronouncements are issued by the FASB or other standard setting bodies that are adopted by the Company as of the specified effective date. Unless otherwise discussed, the Company believes that the impact of recently issued standards that are not yet effective will not have a material impact on the Company's financial position or results of operations upon adoption. The Company adopted Accounting Standard Update (“ASU”) No. 2016-02, Leases (Topic 842), as of January 1, 2019, using the modified retrospective approach with the effective date transition method (note 5). Accordingly, all periods prior to adoption are presented in accordance with legacy accounting and the Company recorded no retrospective adjustments to the comparative periods presented. In addition, the Company elected the package of practical expedients permitted under the transition guidance within ASC 842, which among other things, allowed the Company to carry forward its historical lease classification. In addition, the Company elected the short term exemption, which allows entities to not capitalize their leases with a term of 12 months or less. Adoption of the new standard resulted in the recording of operating lease right-of-use assets (“ROU assets”) and lease liabilities of approximately $3.2 million and $4.1 million , respectively, as of January 1, 2019. The standard did not materially impact the Company’s consolidated statements of operations and statements of cash flow. In November 2018, the FASB issued targeted amendments to ASU No. 2018-18, Collaborative Arrangements (Topic 808), and ASU No. 2016-10, Revenue from Contracts with Customers (Topic 606), to clarify that certain transactions between parties to collaborative arrangements should be accounted for in accordance with FASB revenue guidance when the counterparty is a customer. This guidance also prohibits the presentation of collaborative arrangements as revenues from contracts with customers if the counterparty is not a customer. This guidance, which is required to be applied retrospectively and is effective for interim and annual periods beginning after December 15, 2019, with early adoption permitted, is not expected to have a material impact on the Company’s consolidated financial statements.
Fair value of financial instruments	Fair value of financial instruments The Company measures certain financial instruments and other items at fair value. To determine the fair value, the Company uses the fair value hierarchy for inputs used in measuring fair value that maximizes the use of observable inputs and minimizes the use of unobservable inputs by requiring that the most observable inputs be used when available. Observable inputs are inputs market participants would use to value an asset or liability and are developed based on market data obtained from independent sources. Unobservable inputs are inputs based on assumptions about the factors market participants would use to value an asset or liability. The three levels of inputs that may be used to measure fair value are as follows: • Level 1 inputs are quoted market prices for identical instruments available in active markets. • Level 2 inputs are inputs other than quoted prices included within Level 1 that are observable for the asset or liability either directly or indirectly. If the asset or liability has a contractual term, the input must be observable for substantially the full term. An example includes quoted market prices for similar assets or liabilities in active markets. • Level 3 inputs are unobservable inputs for the asset or liability and will reflect management’s assumptions about market assumptions that would be used to price the asset or liability.

Significant Accounting Polici_3

Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2019
Accounting Policies [Abstract]
Schedule of basic and diluted net income (loss) per common share	The following table sets out the computation of basic and diluted net loss attributable to common shareholders per share: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands, except share and per share amounts) Numerator: Allocation of distributable earnings $ — $ — $ — $ — Allocation of undistributable loss (85,295 ) (27,040 ) (137,338 ) (46,255 ) Allocation of loss attributed to common shareholders $ (85,295 ) $ (27,040 ) $ (137,338 ) $ (46,255 ) Denominator: Weighted average number of common shares - basic and diluted 56,850,172 55,421,504 56,469,358 55,241,284 Basic and diluted net loss attributable to common shareholders per share $ (1.50 ) $ (0.49 ) $ (2.43 ) $ (0.84 )

Fair Value of Financial Instr_2

Fair Value of Financial Instruments (Tables)	9 Months Ended
	Sep. 30, 2019
Fair Value Disclosures [Abstract]
Assets and liabilities measured at fair value on a recurring basis	The following table presents information about the Company’s assets and liabilities that are measured at fair value on a recurring basis, and indicates the fair value hierarchy of the valuation techniques used to determine such fair value: Level 1 Level 2 Level 3 Total As of September 30, 2019 (in thousands) Assets Cash and cash equivalents $ 90,082 $ — $ — $ 90,082 Liabilities Liability-classified options — — 86 86 Contingent consideration — — 3,005 3,005 Total $ — $ — $ 3,091 $ 3,091
Changes in fair value of liability option	The following table presents the changes in fair value of the Company’s liability-classified stock option awards: Liability at beginning of the period Fair value of liability-classified options exercised in the period Increase (decrease) in fair value of liability Liability at end of the period (in thousands) Nine months ended September 30, 2018 $ 1,239 $ — $ 1,499 $ 2,738 Nine months ended September 30, 2019 $ 479 $ — $ (393 ) $ 86
Schedule of changes in fair value of contingent consideration	The following table presents the changes in fair value of the Company’s contingent consideration: Liability at beginning of the period Increase (decrease) in fair value of liability Liability at end of the period (in thousands) Nine months ended September 30, 2018 $ 10,424 $ (6,263 ) $ 4,161 Nine months ended September 30, 2019 $ 3,126 $ (121 ) $ 3,005

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2019
Leases [Abstract]
Schedule of Lease Terms, Discount Rate and Supplemental Cash Flow Information	Weighted average remaining lease term and discount rate were as follows: As of September 30, 2019 Weighted-average remaining lease term (years) 7.3 Weighted average discount rate 8.9% The Company did not include options to extend its lease terms as part of its ROU asset and lease liabilities. Supplemental cash flow information related to the Company's operating leases was as follows: Nine Months Ended September 30, 2019 2018 (in thousands) Cash paid for amounts included in the measurement of lease liabilities $ 921 $ —
Schedule of Maturities of Lease Liabilities	Maturities of lease liabilities were as follows: As of September 30, 2019 (in thousands) October through December 2019 $ 188 2020 657 2021 677 2022 581 2023 598 Thereafter 2,039 Total Lease Payments $ 4,740 Less: interest (1,268 ) Present value of lease payments $ 3,472

Accounts Payable and Accrued _2

Accounts Payable and Accrued Liabilities (Tables)	9 Months Ended
	Sep. 30, 2019
Payables and Accruals [Abstract]
Schedule of accounts payable and accrued liabilities	Accounts payable and accrued liabilities are comprised of the following: September 30, 2019 December 31, 2018 (in thousands) Trade accounts payable $ 1,400 $ 3,192 Research and development accruals 4,112 2,716 Professional fee accruals 1,177 871 Payroll accruals 1,509 2,341 Other accrued liabilities 1 309 $ 8,199 $ 9,429

Site Consolidation (Tables)

Site Consolidation (Tables)	9 Months Ended
	Sep. 30, 2019
Restructuring and Related Activities [Abstract]
Schedule of expenses and reserve recorded for site consolidation	Site consolidation expenses were as follows: Three Months Ended September 30, Nine Months Ended September 30, 2019 2018 2019 2018 (in thousands) Employee severance and relocation $ 231 $ 198 $ 429 $ 3,399 Facility and other expenses (49 ) (690 ) (396 ) 311 Total site consolidation expense $ 182 $ (492 ) $ 33 $ 3,710 Site consolidation activity was as follows: Employee severance and relocation Facility and other expenses Total (in thousands) Site consolidation accrual as of December 31, 2018 $ 697 $ 634 $ 1,331 Additional accruals and other adjustments 429 (396 ) 33 Payments (923 ) (238 ) (1,161 ) Site consolidation accrual as of September 30, 2019 $ 203 $ — $ 203

Sale of Future Royalties (Table

Sale of Future Royalties (Tables)	9 Months Ended
	Sep. 30, 2019
Other Liabilities Disclosure [Abstract]
Schedule of activity related to the net liability from inception of the Agreement	The table below shows the activity related to the net liability from inception of the Agreement through September 30, 2019 : Nine Months Ended September 30, 2019 (in thousands) Net liability related to sale of future royalties - beginning balance $ — Initial recognition of liability 30,000 Debt discount and issuance costs (11,451 ) Non-cash royalty revenue (979 ) Non-cash interest expense 1,106 Net liability related to sale of future royalties - ending balance $ 18,675

Significant Accounting Polici_4

Significant Accounting Policies - Narrative (Details) $ in Thousands, shares in Millions	9 Months Ended
	Sep. 30, 2019USD ($)subsidiaryshares	Sep. 30, 2018shares	Jan. 01, 2019USD ($)	Dec. 31, 2018USD ($)
Accounting Policies [Abstract]
Wholly-owed subsidiaries | subsidiary	2
Anti-dilutive common shares excluded from calculation of loss per common share (in shares) | shares	28.2	24.2
ROU assets	$ 2,817		$ 3,200	$ 0
Lease liabilities	$ 3,143		$ 4,100	$ 0

Significant Accounting Polici_5

Significant Accounting Policies - Schedule of Computation of Basic and Diluted Income (Loss) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Numerator:
Net loss attributable to common shareholders (note 2)	$ (85,295)	$ (27,040)	$ (137,338)	$ (46,255)
Denominator:
Weighted average number of common shares - basic and diluted	56,850,172	55,421,504	56,469,358	55,241,284
Basic and diluted net loss attributable to common shareholders per share	$ (1.50)	$ (0.49)	$ (2.43)	$ (0.84)
Common Shares
Numerator:
Allocation of distributable earnings	$ 0	$ 0	$ 0	$ 0
Allocation of undistributable loss	(85,295)	(27,040)	(137,338)	(46,255)
Net loss attributable to common shareholders (note 2)	$ (85,295)	$ (27,040)	$ (137,338)	$ (46,255)
Denominator:
Weighted average number of common shares - basic and diluted	56,850,172	55,421,504	56,469,358	55,241,284
Basic and diluted net loss attributable to common shareholders per share	$ (1.50)	$ (0.49)	$ (2.43)	$ (0.84)

Fair Value of Financial Instr_3

Fair Value of Financial Instruments - Assets and Liabilities Measured at Fair Value on Recurring Basis (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018	Sep. 30, 2018	Dec. 31, 2017
Liabilities
Contingent consideration (notes 3 and 10)	$ 3,005	$ 3,126	$ 4,161	$ 10,424
Recurring
Assets
Cash and cash equivalents	90,082	36,942
Short-term investments		87,675
Total Assets		124,617
Liabilities
Liability-classified options	86	479
Contingent consideration (notes 3 and 10)	3,005	3,126
Total Liabilities	3,091	3,605
Recurring | Level 1
Assets
Cash and cash equivalents	90,082	36,942
Short-term investments		87,675
Total Assets		124,617
Liabilities
Liability-classified options	0	0
Contingent consideration (notes 3 and 10)	0	0
Total Liabilities	0	0
Recurring | Level 2
Assets
Cash and cash equivalents	0	0
Short-term investments		0
Total Assets		0
Liabilities
Liability-classified options	0	0
Contingent consideration (notes 3 and 10)	0	0
Total Liabilities	0	0
Recurring | Level 3
Assets
Cash and cash equivalents	0	0
Short-term investments		0
Total Assets		0
Liabilities
Liability-classified options	86	479
Contingent consideration (notes 3 and 10)	3,005	3,126
Total Liabilities	$ 3,091	$ 3,605

Fair Value of Financial Instr_4

Fair Value of Financial Instruments - Changes in Fair Value of Liabilities-Classified as Stock Option (Details) - Liability classified stock options - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period	$ 479	$ 1,239
Fair value of liability-classified options exercised in the period	0	0
Increase (decrease) in fair value of liability	(393)	1,499
Liability at end of the period	$ 86	$ 2,738

Fair Value of Financial Instr_5

Fair Value of Financial Instruments - Changes in Fair Value of Contingent Consideration (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Fair Value, Liabilities Measured on Recurring Basis [Roll Forward]
Liability at beginning of the period			$ 3,126	$ 10,424
Increase (decrease) in fair value of liability	$ (376)	$ (5,608)	(121)	(6,263)
Liability at end of the period	$ 3,005	$ 4,161	$ 3,005	$ 4,161

Equity Method Investment (Detai

Equity Method Investment (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended			9 Months Ended
	Apr. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Jun. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Schedule of Equity Method Investments [Line Items]
Gains (losses) on equity method investments		$ (3,512)	$ (2,838)		$ (11,497)	$ (2,838)
Investment in Genevant		10,969			10,969		$ 22,224
Genevant Sciences Corporation
Schedule of Equity Method Investments [Line Items]
Gains (losses) on equity method investments		$ (3,500)		$ 24,900	$ (11,500)
Ownership interest in equity method investment		40.00%			40.00%
Roivant Sciences Ltd | Genevant Sciences Corporation
Schedule of Equity Method Investments [Line Items]
Property contribution to investment in Genevant	$ 37,500

Leases - Narrative (Details)

Leases - Narrative (Details) $ in Millions	9 Months Ended
	Sep. 30, 2019USD ($)leaserenewal_option	Sep. 30, 2018USD ($)
Lessee, Lease, Description [Line Items]
Number of leases | lease	2
Total operating lease expense	$ 1.1
Fixed lease payments	0.9
Variable lease costs	0.2
Straight-line fixed expenses leases	0.9
Sublease income	$ 0.2	$ 0.1
Corporate Headquarters Located 701 Veterans Circle, Warminster, Pennsylvania
Lessee, Lease, Description [Line Items]
Number of renewal options | renewal_option	2
Lease renewal term	5 years
Incremental borrowing rate	9.00%
Offices Located at 626 Jacksonville Rd., Warminster, Pennsylvania [Member]
Lessee, Lease, Description [Line Items]
Incremental borrowing rate	7.60%
Sublease, Burnaby Facility | Genevant Sciences Corporation
Lessee, Lease, Description [Line Items]
Incremental borrowing rate	5.00%

Leases - Weighted Average Remai

Leases - Weighted Average Remaining Lease Term and Discount Rate (Details)	Sep. 30, 2019
Leases [Abstract]
Weighted-average remaining lease term (years)	7 years 3 months 18 days
Weighted average discount rate	8.90%

Leases - Supplemental Cash Flow

Leases - Supplemental Cash Flow Information (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018
Leases [Abstract]
Cash paid for amounts included in the measurement of lease liabilities	$ 921	$ 0

Leases - Maturities of Lease Li

Leases - Maturities of Lease Liabilities (Details) $ in Thousands	Sep. 30, 2019USD ($)
Leases [Abstract]
October through December 2019	$ 188
2020	657
2021	677
2022	581
2023	598
Thereafter	2,039
Total Lease Payments	4,740
Less: interest	(1,268)
Present value of lease payments	$ 3,472

Intangible Assets and Goodwill

Intangible Assets and Goodwill (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Indefinite-lived Intangible Assets [Line Items]
Impairment of intangible assets	$ 43,836,000	$ 14,811,000	$ 43,836,000	$ 14,811,000
Intangible assets	0		0		$ 43,836,000
Impairment of goodwill	22,471,000	$ 0	22,471,000	$ 0
Goodwill	0		0		$ 22,471,000
IPR&D – cccDNA
Indefinite-lived Intangible Assets [Line Items]
Impairment of intangible assets	43,800,000
Intangible assets	0		$ 0
Tax benefit related to decrease in deferred tax liability for indefinite delay of further development) Liability	$ 12,700,000

Accounts Payable and Accrued _3

Accounts Payable and Accrued Liabilities (Details) - USD ($) $ in Thousands	Sep. 30, 2019	Dec. 31, 2018
Payables and Accruals [Abstract]
Trade accounts payable	$ 1,400	$ 3,192
Research and development accruals	4,112	2,716
Professional fee accruals	1,177	871
Payroll accruals	1,509	2,341
Other accrued liabilities	1	309
Accounts payable and accrued liabilities	$ 8,199	$ 9,429

Site Consolidation - Narrative

Site Consolidation - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		21 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Site consolidation (note 8)	$ 182	$ (492)	$ 33	$ 3,710	$ 4,800
Facility closing
Restructuring Cost and Reserve [Line Items]
Expected total cost of site consolidation	5,000		5,000		$ 5,000
Site consolidation (note 8)	$ (49)	$ (690)	$ (396)	$ 311

Site Consolidation - Consolidat

Site Consolidation - Consolidation Expenses (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		21 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019
Restructuring Cost and Reserve [Line Items]
Total site consolidation expense	$ 182	$ (492)	$ 33	$ 3,710	$ 4,800
Employee severance and relocation
Restructuring Cost and Reserve [Line Items]
Total site consolidation expense	231	198	429	3,399
Facility and other expenses
Restructuring Cost and Reserve [Line Items]
Total site consolidation expense	$ (49)	$ (690)	$ (396)	$ 311

Site Consolidation - Reserve Ac

Site Consolidation - Reserve Activity (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		21 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019
Restructuring Reserve [Roll Forward]
Site consolidation accrual as of December 31, 2018			$ 1,331
Additional accruals and other adjustments	$ 182	$ (492)	33	$ 3,710	$ 4,800
Payments			(1,161)
Site consolidation accrual as of September 30, 2019	203		203		203
Employee severance and relocation
Restructuring Reserve [Roll Forward]
Site consolidation accrual as of December 31, 2018			697
Additional accruals and other adjustments	231	198	429	3,399
Payments			(923)
Site consolidation accrual as of September 30, 2019	203		203		203
Facility and other expenses
Restructuring Reserve [Roll Forward]
Site consolidation accrual as of December 31, 2018			634
Additional accruals and other adjustments	(49)	$ (690)	(396)	$ 311
Payments			(238)
Site consolidation accrual as of September 30, 2019	$ 0		$ 0		$ 0

Sale of Future Royalties - Narr

Sale of Future Royalties - Narrative (Details) - USD ($) $ in Thousands	Jul. 02, 2019	Jan. 01, 2019	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Other Liabilities Disclosure [Line Items]
Non-cash royalty revenue			$ 979	$ 0	$ 979	$ 0
Non-cash interest expense			1,106	$ 0	$ 1,106	$ 0
OMERS
Other Liabilities Disclosure [Line Items]
Annual royalty revenue	$ 500,000
Gross proceeds from sale of royalty interest. before advisory fees		$ 20,000
Entitlement of royalties to be received	$ 30,000
Royalty guarantees commitments percentage	100.00%
Future royalty payments	$ 30,000
Transaction costs on sale of royalties	$ 1,500
Effective annual interest rate on royalty liability	25.00%
Non-cash royalty revenue			1,000
Non-cash interest expense			$ 1,100
OMERS | Minimum
Other Liabilities Disclosure [Line Items]
Royalty interest sold percentage	1.00%
OMERS | Maximum
Other Liabilities Disclosure [Line Items]
Royalty interest sold percentage	2.33%

Sale of Future Royalties - Liab

Sale of Future Royalties - Liability Activity (Details) $ in Thousands	3 Months Ended
	Sep. 30, 2019USD ($)
Liability Related To Sale Of Future Royalties [Roll Forward]
Net liability related to sale of future royalties - beginning balance	$ 0
Initial recognition of liability	30,000
Debt discount and issuance costs	(11,451)
Non-cash royalty revenue	(979)
Non-cash interest expense	1,106
Net liability related to sale of future royalties - ending balance	$ 18,675

Contingencies and Commitments (

Contingencies and Commitments (Details)	Aug. 20, 2019USD ($)	Jan. 16, 2015USD ($)	Nov. 30, 2018USD ($)	Jun. 30, 2017USD ($)Legal_proceedings	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2018USD ($)	Dec. 31, 2018USD ($)	Dec. 31, 2017USD ($)	Oct. 31, 2014USD ($)patentproduct
Contingencies and Commitments [Line Items]
Arbitration settlement charges					$ 6,486,000	$ 0	$ 6,486,000	$ 0
Fair value of contingent consideration					3,005,000	$ 4,161,000	3,005,000	$ 4,161,000	$ 3,126,000	$ 10,424,000
Arbutus Inc. | Enantigen
Contingencies and Commitments [Line Items]
Business combination, high end of payment upon achievement of certain triggering events											$ 21,000,000
Number of products covered by patent acquired under the agreement | product											2
Development and regulatory milestones payment per licensed compound series, maximum											$ 500,000
Blumberg and Drexel | Arbutus Inc.
Contingencies and Commitments [Line Items]
Development and regulatory milestones payment per licensed compound series, maximum											102,500,000
Development and regulatory milestones payment per royalty, maximum											$ 1,000,000
Number of patent license agreements | patent											3
Blumberg | Arbutus Inc.
Contingencies and Commitments [Line Items]
Research funding period			2 years
Research funding per year under research collaboration and funding agreement			$ 800,000
Recurring
Contingencies and Commitments [Line Items]
Fair value of contingent consideration					3,005,000		3,005,000		$ 3,126,000
Recurring | Blumberg and Drexel | Enantigen
Contingencies and Commitments [Line Items]
Fair value of contingent consideration					3,000,000		3,000,000
Arbitration with the University of British Columbia
Contingencies and Commitments [Line Items]
Loss contingency, damages sought for allegedly unpaid royalties		$ 3,500,000		$ 10,900,000
Number of legal proceedings | Legal_proceedings				3
Arbitration settlement, amount awarded to other party	$ 5,900,000				5,900,000
Arbitration settlement interest	2,600,000
Arbitration settlement charges					6,500,000
Arbitration settlement payment	$ 5,900,000
Arbitration with the University of British Columbia | Minimum
Contingencies and Commitments [Line Items]
Estimate of potential arbitration award for costs and attorney's fees					$ 600,000		$ 600,000

Collaborations, Contracts and_2

Collaborations, Contracts and Licensing Agreements (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue	$ 3,061	$ 1,587	$ 4,393	$ 4,267
Royalties | Gritstone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue	$ 1,500		$ 1,500
License | Gritstone
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenue		$ 1,300		$ 1,300

Stockholders' Equity and Stoc_2

Stockholders' Equity and Stock-based Compensation (Details) - USD ($)	1 Months Ended		3 Months Ended					9 Months Ended
	Jan. 31, 2018	Oct. 31, 2017	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Class of Stock [Line Items]
Proceeds from issuance of shares under the agreement			$ 0			$ 0		$ 4,725,000	$ 0
Issuance of common shares pursuant to the agreement				$ 2,477,000	$ 2,248,000		$ 66,265,000
Proceeds from sale of stock			$ 0			$ 0		$ 0	$ 66,265,000
Preferred Shares
Class of Stock [Line Items]
Shares issued (in shares)		1,164,000
Roivant Sciences Ltd
Class of Stock [Line Items]
Ownership percentage by noncontrolling owners after conversion		49.00%
Maximum ownership percentage by noncontrolling owners		49.99%
Proceeds from sale of stock	$ 66,400,000	$ 50,000,000
Roivant Sciences Ltd | Convertible Preferred Stock
Class of Stock [Line Items]
Issuance of common shares pursuant to the agreement		$ 116,400,000
Preferred stock dividend rate as a percent		8.75%						8.75%
Preferred stated value (in dollars per share)		$ 7.13
Number of common shares to be issued upon conversion of convertible preferred stock		0
Investment commitment period		4 years
Open Market Sale Agreement | Jefferies LLC | Common Shares
Class of Stock [Line Items]
Aggregate sale price of common shares under agreement										$ 50,000,000
Number of shares issued under agreement (in sales)			0					1,208,090
Proceeds from issuance of shares under the agreement								$ 5,200,000

Related Party Transaction (Deta

Related Party Transaction (Details) - Genevant Sciences Corporation - Equity Method Investee	3 Months Ended		9 Months Ended
	Sep. 30, 2019USD ($)ft²	Sep. 30, 2018USD ($)	Sep. 30, 2019USD ($)ft²	Sep. 30, 2018USD ($)
Research and development services
Related Party Transaction [Line Items]
Expenses from transactions with related party	$ 0	$ 100,000	$ 33,000	$ 200,000
Administrative And Transitional Services
Related Party Transaction [Line Items]
Income from related party	0	$ 100,000	284,000	$ 300,000
Sublease, Burnaby Facility
Related Party Transaction [Line Items]
Income from related party	$ 21,000		$ 100,000
Area of sublease facility | ft²	17,900		17,900