Acquisition - Summary of Fair Values of Assets Acquired and Liabilities Assumed (Details) - USD ($) $ in Thousands	Dec. 31, 2017	Nov. 07, 2017
Business Acquisition [Line Items]
Goodwill	$ 44,406
Dimension
Business Acquisition [Line Items]
Cash and cash equivalents		$ 12,338
Short-term investments		9,737
Other current assets		11,155
Property and equipment		6,580
In-process research and development		129,000
Bayer collaboration agreement		13,526
Accounts payable and accrued liabilities		(10,265)
Notes payable		(4,944)
Deferred tax liabilities		(47,412)
Net identifiable net assets acquired		119,715
Goodwill		44,406
Net assets acquired		$ 164,121