Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended			24 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2017
Other Commitments [Line Items]
Gross rent expense	$ 4,000	$ 3,900	$ 4,100
Financing obligation on leased facility	92,009	93,385		$ 93,385
Non-cancellable purchase orders for procurement of goods and services to be received through 2021	15,700
Standby letters of credit issued	$ 7,800
San Mateo Facility
Other Commitments [Line Items]
Finance lease expiration period	Dec. 31, 2028
Capitalized construction costs			71,800
Leasehold improvement costs reimbursed by landlord		6,800	$ 7,500	14,300
Financing obligation on leased facility	$ 92,000	$ 93,400		$ 93,400
Palo Alto Lease Termination
Other Commitments [Line Items]
Finance lease expiration period	Mar. 31, 2026
Derecognized the building’s net book value	$ 60,100
New lessee for sale of certain property and equipment	3,000
Recognized gain on sale of property	$ 900