Major Customers, Partnerships and Strategic Alliances - Revenues Recognized under Agreement (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	$ 21,958	$ 23,562	$ 47,577	$ 57,615
Kite Pharma Inc
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	8,861	9,028	26,233	16,544
Kite Pharma Inc | Collaboration Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	6,296	6,296	18,682	12,249
Kite Pharma Inc | Research Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	2,565	2,732	7,551	4,295
Pfizer SB-525 | Collaboration Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	3,440	10,421	5,035	26,262
Pfizer | Collaboration Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	468	394	1,538	1,470
Sanofi
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	2,754	2,240	7,763	11,139
Sanofi | Collaboration Agreements
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	940	1,094	2,594	3,432
Sanofi | Research Services
Research and Development Arrangement, Contract to Perform for Others [Line Items]
Revenues	$ 1,814	$ 1,146	$ 5,169	$ 7,707