Collaboration and License Agreements - General Information (Details) $ in Thousands				1 Months Ended					3 Months Ended				6 Months Ended		12 Months Ended
	Jul. 13, 2020 USD ($)	Oct. 15, 2019 USD ($) item	Jun. 01, 2018 USD ($) item	Jul. 31, 2020 USD ($)	Oct. 31, 2019 USD ($)	Jun. 30, 2018 USD ($)	Mar. 31, 2018 USD ($)	Mar. 31, 2016 USD ($) item	Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) item	Jun. 30, 2019 USD ($)	Jun. 30, 2018 USD ($)	Jun. 30, 2020 USD ($) Milestone	Jun. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)
Collaboration Agreements
Collaboration revenue									$ 8,343		$ 5,110		$ 14,510	$ 5,840
Current portion of deferred revenue									$ 8,017	$ 6,160			$ 8,017		$ 6,160
Roche | Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2020-07-01
Collaboration Agreements
Research and development services, performance period									4 years 9 months 18 days				4 years 9 months 18 days
Collaboration | Clementia
Collaboration Agreements
Non-refundable upfront payment received		$ 25,000
Milestone payment received					$ 20,000
Cash milestone payment		20,000							$ 20,000	20,000			$ 20,000		20,000
Milestone other payment		490,000
Purchase specified manufacturing inventory		$ 1,500
Number of performance obligations | item		3
Purchase of existing manufacturing inventory		$ 1,200
Purchase of in-process manufacturing inventory		$ 300
Number of material promises | item		4
Initial cash payment		$ 46,500
Collaboration revenue									300		0		300	0	46,200
Deferred revenue									0	0			0		0
Collaboration | Clementia | Subsequent Event
Collaboration Agreements
Milestone payment received				$ 20,000
Collaboration | C Stone
Collaboration Agreements
Non-refundable upfront payment received			$ 40,000									$ 40,000
Eligible milestone payments			$ 346,000
Number of performance obligations | item			3
Licensed product term from first commercial sale			12 years
Number of materials components | item			2
Number of option rights to obtain exclusive license | item			3
Number of potential collaboration programs | item			3
Number of material promises | item			6
Number of collaboration programs with exclusive commercialization rights for licensed products | item			3
Initial cash payment			$ 40,000
Collaboration revenue									1,263		4,144		3,397	4,144
Deferred revenue									0	$ 0			$ 0		$ 0
Collaboration | C Stone | Development and regulatory milestones
Collaboration Agreements
Eligible milestone payments			118,500
Number of milestones acheived | Milestone													1
Collaboration revenue													$ 2,000
Collaboration | C Stone | Sales-based milestones
Collaboration Agreements
Eligible milestone payments			$ 227,500
Collaboration | Roche
Collaboration Agreements
Non-refundable upfront payment received								$ 45,000
Number of small molecule therapeutics targeting kinases | item								5
Number of option rights to obtain exclusive license | item								5
Number of potential collaboration programs | item								4		4
Initial cash payment							$ 45,000	$ 45,000
Collaboration revenue									1,109		966		1,684	1,697
Deferred revenue									44,700				44,700
Total eligible contingent option fees and milestone payments								940,000
Eligible option fees and milestones prior to licensing for all potential collaboration programs								$ 190,000
Current portion of deferred revenue									8,000				8,000
Achieved research milestone payment received which will be recognized over period of performance					$ 8,000	$ 10,000
Revenue recognized, change in contract liability									$ 1,061		$ 966		$ 2,050	$ 1,953
Collaboration | Roche | Subsequent Event
Collaboration Agreements
Non-refundable upfront payment received	$ 675,000
Total eligible contingent option fees and milestone payments	$ 927,000
Collaboration | Roche | Prior To Exercise License Right Option
Collaboration Agreements
Written termination notice period								120 days
Collaboration | Roche | Exercise Of License Right Option
Collaboration Agreements
Number of collaboration programs with exclusive commercialization rights for licensed products | item								2
Number of collaboration programs with specified commercial rights for each party | item								2
Collaboration | Roche | Exercise Of License Option Product Not Commercially Sold
Collaboration Agreements
Written termination notice period								120 days
Collaboration | Roche | Exercise Of License Option Product Commercially Sold
Collaboration Agreements
Written termination notice period								180 days