Sutro Biopharma, Inc. Annual report pursuant to Section 13 and 15(d)

Annual report pursuant to Section 13 and 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	12 Months Ended
	Feb. 29, 2020 USD ($)	Oct. 31, 2020 USD ($)	Aug. 31, 2020 USD ($)	Mar. 31, 2020 USD ($)	Feb. 29, 2020 USD ($)	Sep. 30, 2019 USD ($)	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 ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Dec. 31, 2014 USD ($)	Jan. 01, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payments of embedded derivative and related liability																		$ 200,000	$ 100,000
EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
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.
Celgene Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of programs advancing through preclinical development \| Program												4
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
Deferred revenue												8,200,000						$ 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																		3,000,000.0	3,900,000	$ 16,600,000
Partially Unsatisfied Performance Obligations \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue																		0	3,800,000
Research and Development Services
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue																		600,000	600,000	100,000
Research and Development Services \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue																		0	1,700,000	3,100,000
2018 Celgene Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue																		1,200,000	0
Other revenue-related parties																		7,800,000	6,800,000	4,500,000
2018 Merck Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue																		18,500,000	31,900,000
Number of research programs \| Program									2
Upfront payment received									$ 60,000,000.0
Revenue recognized performance obligation																	$ 47,100,000
Transaction price																	60,000,000.0
2018 Merck Agreement \| Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Embedded interest associated with upfront payment																		1,900,000	3,100,000	0
FTE Funding Received																		5,500,000	3,600,000	1,500,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| Partially Unsatisfied Performance Obligations
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue																		18,500,000	14,700,000	7,000,000.0
2018 Merck Agreement \| Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Number of research programs \| Program										3
Upfront payment received									60,000,000.0									60,000,000.0
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)
Revenue recognition aggregate contingent payments eligible to receive																		$ 500,000,000
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 \| ASC 606 \| Celgene
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 \| ASC 606 \| Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total interest of unearned revenue																		$ 7,300,000
First Cytokine-Derivative Program \| Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Revenue, remaining performance obligation, amount				0													0
Upfront payment received				5,000,000.0
Recognition of up front payment				$ 50,500,000													50,500,000
Extended research term				1 year
Transaction price	$ 60,000,000.0			$ 65,000,000.0
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
2020 Merck Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue																		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]
Contingent payment received						$ 1,500,000
Milestone payment received		$ 1,000,000.0
Up-front, nonrefundable and non-creditable payment received															$ 10,000,000.0
Maximum amount eligible to receive for each product developed																		52,500,000
Clinical supply milestone payment earned			$ 1,000,000.0
Performance Under Deliverables \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue																				4,100
2019 EMD Serono Supply Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue																		1,000,000.0	800,000
Total revenue																		4,000,000.0	3,400,000
Supply Agreement \| Vaxcyte
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue																		$ 200,000	$ 1,100,000	$ 1,500,000
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