Commitments and Contingencies - Additional Information (Details) - USD ($)	1 Months Ended		12 Months Ended
	Dec. 31, 2019	Dec. 31, 2016	Dec. 31, 2018	Jun. 30, 2020	Apr. 30, 2020
Indenix
Loss Contingencies [Line Items]
Damages awarded		$ 2,540,000,000
Past damages vacated			$ 2,540,000,000
Juno
Loss Contingencies [Line Items]
Damages awarded	$ 585,000,000
Running royalty rate on future sales	27.60%				27.60%
Enhancement rate on past damages					50.00%
Estimate of possible loss representing past sales				$ 811,000,000
Estimate of possible loss representing enhancement of past damages				389,000,000
Estimate of possible loss representing royalties and prejudgment interest				88,000,000
Juno | Minimum
Loss Contingencies [Line Items]
Estimate of possible loss				0
Juno | Maximum
Loss Contingencies [Line Items]
Estimate of possible loss				$ 1,300,000,000