Commitments and Contingencies (Details)	Mar. 01, 2019 USD ($)	Dec. 03, 2018 USD ($) day	Apr. 19, 2018 USD ($)
Severance restricted stock units, weighted average price, number of trading days \| day		20
Minimum
Exercise period of stock options			90 days
Maximum
Exercise period of stock options			2 years
Mr. Mould
Severance benefits		$ 900,000
Severance benefits, period of consideration		2 years
Cash severance payment		$ 100,000
Restricted stock units awarded as part of severance		21 months
Common shares, volume weighted-average price	$ 33,333
Dr. Stephen Clarke \| Employment Agreement
Severance benefits			$ 900,000
Severance benefits, period of consideration			2 years
Expense related to stock option awards			$ 15,000,000