Sutro Biopharma, Inc. Quarterly report pursuant to Section 13 or 15(d)

Quarterly report pursuant to Section 13 or 15(d)

Collaboration and License Agreements and Supply Agreements - Additional Information (Details)

Collaboration and License Agreements and Supply Agreements - Additional Information (Details)	1 Months Ended													3 Months Ended			9 Months Ended
	Apr. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	May 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Aug. 31, 2018 USD ($) Program	Jul. 31, 2018 Program	Sep. 30, 2017 USD ($)	Aug. 31, 2017 USD ($) Program	Jun. 30, 2016 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	May 31, 2014 USD ($)	Sep. 30, 2020 USD ($)	Mar. 31, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Dec. 31, 2019 USD ($)	Jan. 01, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payments of embedded derivative and related liability														$ 200,000			$ 200,000		$ 100,000
EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Recognition of up front payment														20,000,000.0			20,000,000.0
Changes in deferred revenue																	$ 600,000
The Leukemia & Lymphoma Society, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Research development and commercialization agreement termination period																	12 years
Research development and commercialization agreement termination description																	The LLS Agreement terminates upon the earlier of (a) fulfillment of all payment obligations by both parties or (b) 12 years after the effective date. LLS may terminate the LLS Agreement at any time with 60 days’ prior written notice. Either the Company or LLS has the right to terminate the LLS Agreement based on the other party’s uncured material breach.
First Cytokine-Derivative Program \| Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Extended research term		1 year
Upfront payment received		$ 5,000,000.0
Revenue, remaining performance obligation, amount		0													$ 0
Recognition of up front payment		50,500,000													50,500,000
Transaction price		65,000,000.0	$ 60,000,000.0
Constrained variable consideration			$ 5,000,000.0
Revenue reallocated property rights		7,800,000
Incremental revenue recognized reallocated target programs		$ 500,000
Estimated service period		3 years
Incremental revenue recognized		$ 1,500,000
Adjustments to transaction price		5,900,000
Cumulative catch-up in revenue															2,000,000.0
Development and Manufacturing Services \| Vaxcyte, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received	$ 200,000
Celgene Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront, nonrefundable payment received												$ 83,100,000
Contingent payment received											$ 15,000,000.0
Milestone payment received										$ 25,000,000.0
Additional milestone payment received										$ 10,000,000.0
Option fee payment received									$ 12,500,000
Milestone revenue recognized					$ 10,000,000.0			$ 10,000,000.0
Contingent payments				$ 275,000,000.0
Option maintenance fee									$ 12,500,000
Number of programs advancing through preclinical development \| Program									4
Deferred revenue									$ 8,200,000					0			$ 0		3,000,000.0
Revenue, remaining performance obligation, amount									20,700,000
Celgene Agreement \| ASC 606 \| Difference between Revenue Guidance in Effect before and after Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue																				$ (4,500,000)
Celgene Agreement \| First Performance Obligation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation, amount									8,200,000
Celgene Agreement \| Future Services on Collaboration Joint Steering Committee ("JSC")
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation, amount									200,000
Celgene Agreement \| Third Performance Obligation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation, amount									$ 12,300,000
Partially Unsatisfied Performance Obligations
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue														1,000,000.0		$ 1,000,000.0	3,000,000.0	$ 2,900,000
Partially Unsatisfied Performance Obligations \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue																1,500,000		3,800,000
Research and Development Services
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue														200,000		100,000	600,000	400,000
Research and Development Services \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue														300,000		500,000	1,100,000	2,200,000
2018 Celgene Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Other revenue-related parties														5,900,000		2,200,000	7,100,000	3,200,000
2018 Merck Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received						$ 60,000,000.0
Deferred revenue														23,900,000			23,900,000		31,900,000
Number of research programs \| Program						2
Revenue recognized performance obligation															47,100,000
Transaction price															$ 60,000,000.0
2018 Merck Agreement \| ASC 606 \| Celgene Corporation
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Changes in deferred revenue due to adoption of new accounting policy																				$ 6,300,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront payment received						$ 60,000,000.0											60,000,000.0
Number of research programs \| Program							3
Revenue from first performance obligation						7,300,000
Recognition of up front payment						47,100,000
Revenue recognized performance obligation						700,000
Extension option fee associated with contingent program						4,900,000
Increase (decrease) in revenue		(5,100,000)
Embedded interest associated with upfront payment														400,000		800,000	1,500,000	2,500,000
FTE Funding Received														1,700,000		900,000	4,200,000	2,600,000
Revenue recognition aggregate milestone payments eligible to receive																	$ 1,600,000,000
Milestone method revenue recognition description																	If one or more products from each of the target programs are developed for non-oncology or a single indication, the Company will be eligible for reduced aggregate milestone payments. In addition, the Company is eligible to receive tiered royalties ranging from mid-single digit to low teen percentages on the worldwide sales of any commercial products that may result from the collaboration.
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| First Target Program
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Increase (decrease) in revenue		(6,200,000)
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| Second Target Program
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Increase (decrease) in revenue		$ 1,100,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| Partially Unsatisfied Performance Obligations
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue														6,900,000		3,800,000	$ 13,000,000.0	10,500,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| ASC 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total interest of unearned revenue														7,300,000			7,300,000
Collaboration Agreement \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front, nonrefundable and non-creditable payment received													$ 10,000,000.0
MDA Agreement \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue														0			0		$ 800,000
Up-front, nonrefundable and non-creditable payment received												$ 10,000,000.0
Maximum amount eligible to receive for each product developed																	52,500,000
Milestone Payment and Supply Agreement \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue														300,000		600,000	2,600,000	2,100,000
Milestone Payment \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue														1,000,000.0			1,000,000.0
Supply Agreement \| Vaxcyte, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue														$ 200,000		$ 800,000	$ 300,000	$ 1,100,000
Research Development and Commercialization Agreement \| The Leukemia & Lymphoma Society, Inc.
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Milestone payment received						1,000,000.0
Maximum contribution in clinical development						6,000,000.0
Initial milestone payment						500,000
Maximum aggregate payment						$ 19,500,000