Leases - Additional Information (Details) ft² in Thousands	12 Months Ended
	Dec. 31, 2019 ft² renewal_option	Dec. 31, 2015 ft² term	Dec. 31, 2011 ft² lease building
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Number of leases | lease			2
Area of real estate property (in square feet)			1,100
Lease agreements number of buildings | building			2
Option to extend lease term			15 years
Optional term of lease agreement (in years)			10 years
San Diego Lease
Lessee, Lease, Description [Line Items]
Area of real estate property (in square feet)		170
Length of lease		16 years
Amount of optional renewal terms | term		2
Optional renewal term length		5 years
Jeffrey Leiden Center for Cell and Genetic Therapies
Lessee, Lease, Description [Line Items]
Area of real estate property (in square feet)	269
Optional term of lease agreement (in years)	10 years
Lease agreement initial term	16 years
Number of optional renewal terms | renewal_option	2