Commitments and Contingencies - Additional Information (Details) $ in Thousands			12 Months Ended
	Sep. 03, 2019 USD ($)	Oct. 04, 2018 USD ($) ft² Right	Dec. 31, 2019 USD ($)
Operating Leased Assets [Line Items]
Operating lease, cost			$ 11,300
Operating lease, payments			$ 7,900
Option to extend, amount | Right		1
Operating lease, weighted average remaining lease term			11 years 7 months 6 days
Operating Lease, weighted average discount rate (in percentage)			736.00%
Verily Life Sciences LLC
Operating Leased Assets [Line Items]
Collaboration agreement, remaining term of agreement	24 months
Collaboration agreement, upfront fee payable			$ 5,000
Collaboration agreement, additional milestone payments, due in next 24 months	$ 12,750
Collaboration agreement, milestone payments paid			1,000
Collaboration agreement, research and development expense			$ 6,000
Office Lease | San Francisco
Operating Leased Assets [Line Items]
Lease rentable area | ft²		117,560
Renewal term of lease		5 years
Office Lease | San Francisco | Standby Letters of Credit
Operating Leased Assets [Line Items]
Credit facility borrowing capacity		$ 6,900
Office Lease | San Francisco | Maximum
Operating Leased Assets [Line Items]
Tenant improvement allowance		$ 2,400