Collaborative Research and Development Agreements (Details)	1 Months Ended		3 Months Ended												6 Months Ended	12 Months Ended
	Nov. 30, 2014 USD ($) target	Mar. 31, 2014 USD ($) target	Mar. 31, 2020 USD ($) milestone	Dec. 31, 2019 USD ($)	Mar. 31, 2019 USD ($)	Sep. 30, 2018 USD ($)	Dec. 31, 2017 USD ($)	Jun. 30, 2017 USD ($)	Dec. 31, 2016 USD ($)	Sep. 30, 2016 USD ($)	Jun. 30, 2016 USD ($)	Mar. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2019 USD ($)	Dec. 31, 2011 USD ($)
Deferred Revenue Arrangement [Line Items]
Collaboration revenue			$ 15,000,000		$ 0
TESARO | Collaborative Research And Development Agreement
Deferred Revenue Arrangement [Line Items]
Upfront license fee received	$ 2,000,000.0	$ 17,000,000.0
Number of outstanding research and development targets | target	4	3
Milestone payments, contingent upon preclinical and clinical trial events (up to)	$ 18,000,000.0
Milestone payments, contingent upon certain U.S. and European regulatory submissions and approvals (up to)	90,000,000.0
Milestone payments, contingent upon achievement of specified levels of worldwide sales (up to)	$ 165,000,000.0
Agreement term following first commercial sale or expiration of the last to expire patent (in years)	12 years
Number of milestones achieved during period | milestone			2
Collaboration revenue			$ 15,000,000.0		0.0
TESARO | Initiated in vivo toxicology studies using good laboratory practices (GLPs) | Anti-PD-1 (TSR042/Dostarlimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount														$ 1,000,000.0
TESARO | Initiated in vivo toxicology studies using good laboratory practices (GLPs) | Anti-TIM-3 (TSR022/Cobolimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount													$ 1,000,000.0
TESARO | Initiated in vivo toxicology studies using good laboratory practices (GLPs) | Anti-LAG-3 (TSR033/Encelimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount										$ 1,000,000.0
TESARO | IND clearance from the FDA | Anti-PD-1 (TSR042/Dostarlimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount												$ 4,000,000.0
TESARO | IND clearance from the FDA | Anti-TIM-3 (TSR022/Cobolimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount											$ 4,000,000.0
TESARO | IND clearance from the FDA | Anti-LAG-3 (TSR033/Encelimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount								$ 4,000,000.0
TESARO | Phase 2 clinical trial initiation | Anti-PD-1 (TSR042/Dostarlimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount								$ 3,000,000.0
TESARO | Phase 2 clinical trial initiation | Anti-TIM-3 (TSR022/Cobolimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount							$ 3,000,000.0
TESARO | Phase 2 clinical trial initiation | Anti-LAG-3 (TSR033/Encelimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount				$ 3,000,000.0
TESARO | Phase 3 clinical trial initiation | Anti-PD-1 (TSR042/Dostarlimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount			15,000,000.0			$ 5,000,000.0
TESARO | Phase 3 clinical trial initiation - second indication [Domain] | Anti-PD-1 (TSR042/Dostarlimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount															$ 5,000,000.0
TESARO | Filing of the first NDA - first indication | Anti-PD-1 (TSR042/Dostarlimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount			10,000,000.0
TESARO | Filing of the first MAA - first indication | Anti-PD-1 (TSR042/Dostarlimab)
Deferred Revenue Arrangement [Line Items]
Milestones achieved, amount			5,000,000.0
Celgene Corporation | Collaborative Research And Development Agreement
Deferred Revenue Arrangement [Line Items]
Upfront license fee received																$ 6,000,000.0
Collaboration revenue			$ 0		$ 0
Maximum milestone payments per target																$ 53,000,000.0
Celgene Corporation | Initiated in vivo toxicology studies using good laboratory practices (GLPs) | Anti-PD-1 (CC-90006)
Deferred Revenue Arrangement [Line Items]
Milestone Event											$ 500,000
Celgene Corporation | Phase 1 clinical trial initiation | Anti-PD-1 (CC-90006)
Deferred Revenue Arrangement [Line Items]
Milestone Event									$ 1,000,000.0