Contingencies and Commitments (Details)		1 Months Ended		3 Months Ended
	Jan. 16, 2015 USD ($)	Nov. 30, 2018 USD ($)	Jun. 30, 2017 Legal_proceedings	Sep. 30, 2019 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2018 USD ($)	Jun. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Oct. 31, 2014 USD ($) patent product
Contingencies and Commitments [Line Items]
Fair value of contingent consideration					$ 3,381,000	$ 3,126,000	$ 9,769,000	$ 10,424,000
Arbitration with the University of British Columbia
Contingencies and Commitments [Line Items]
Loss contingency, damages sought for allegedly unpaid royalties	$ 3,500,000
Number of legal proceedings | Legal_proceedings			3
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
Scenario, Forecast | Arbitration with the University of British Columbia
Contingencies and Commitments [Line Items]
Loss contingency, damages sought for allegedly unpaid royalties				$ 10,900,000
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 per year under research collaboration and funding agreement		$ 800,000
Research funding period		2 years
Recurring
Contingencies and Commitments [Line Items]
Fair value of contingent consideration					3,381,000	3,126,000
Level 3 | Recurring
Contingencies and Commitments [Line Items]
Fair value of contingent consideration					3,381,000	$ 3,126,000
Level 3 | Recurring | Blumberg and Drexel | Enantigen
Contingencies and Commitments [Line Items]
Fair value of contingent consideration					$ 3,400,000