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
	Oct. 01, 2018 USD ($) $ / shares shares	May 31, 2019 USD ($)	Dec. 31, 2018 USD ($)	Aug. 31, 2018 USD ($)	Jul. 31, 2018 Program	Sep. 30, 2017 USD ($)	Aug. 31, 2017 USD ($) Program	Jun. 30, 2016 USD ($)	Mar. 31, 2015 USD ($)	Sep. 30, 2014 USD ($)	May 31, 2014 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Jan. 01, 2019 USD ($)
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Receivables from agreement			$ 2,489,000									$ 7,531,000		$ 7,531,000
Proceeds from issuance of redeemable convertible preferred stock gross														0	$ 84,739,000
Accounts receivable, net			2,489,000
Accounts receivable, related parties			959,000									2,059,000		2,059,000
EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue												2,600,000		8,100,000
Recognition of up front payment												20,000,000		20,000,000
Changes in deferred revenue														600,000
Accounts receivable, net			900,000									5,200,000		5,200,000
SutroVax
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Receivables from agreement			49,000									800,000		800,000
Accounting Standards Update 2014-09
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Accounts receivable, net																$ 2,489,000
Celgene Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Upfront, nonrefundable payment received										$ 83,100,000
Contingent payment received									$ 15,000,000
Milestone payment received								$ 25,000,000
Additional milestone payment received								$ 10,000,000
Option fee payment received							$ 12,500,000
Milestone revenue recognized			10,000,000			$ 10,000,000
Contingent payments		$ 275,000,000
Option maintenance fee							$ 12,500,000
Number of programs advancing through preclinical development \| Program							4
Deferred revenue			11,400,000				$ 8,200,000					4,000,000		4,000,000
Revenue, remaining performance obligation, amount							20,700,000
Receivables from agreement			600,000									0		0
Celgene Agreement \| Accounting Standards Update 2014-09 \| Difference between Revenue Guidance in Effect before and after Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue																(4,500,000)
Total revenue												1,100,000		3,300,000
Celgene Agreement \| ASC 605 \| Difference between Revenue Guidance in Effect before and after Topic 606
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue													$ 1,600,000		5,000,000
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
2018 Celgene Master Services Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Receivables from agreement			0									300,000		300,000
Other revenue-related parties												2,200,000	300,000	3,200,000	3,900,000
2018 Merck Agreement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Deferred revenue			53,000,000									36,100,000		36,100,000
Receivables from agreement			900,000									1,200,000		1,200,000
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										60,000,000
Revenue from first performance obligation				7,300,000
Recognition of up front payment				47,100,000
Revenue performance obligation amounts recognized in revenues				700,000
Extension option fee associated with contingent program				$ 4,900,000
Embedded interest associated with upfront payment												800,000		2,500,000
FTE Funding Received												900,000		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 \| Common Stock \| Private Placement
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Stock Issued, shares \| shares	666,666
Share issue price per share \| $ / shares	$ 15.00
Proceeds from issuance of common stock	$ 10,000,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| Series E Redeemable Convertible Preferred Stock
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Stock Issued, shares \| shares	74,794,315
Share issue price per share \| $ / shares	$ 0.2674
Proceeds from issuance of redeemable convertible preferred stock gross	$ 20,000,000
2018 Merck Agreement \| Merck Sharp & Dohme Corp \| Collaboration Revenue, Amortization of Up-front Payment
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue												3,800,000		$ 10,500,000
2018 Merck Agreement \| Accounting Standards Update 2014-09 \| 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 \| Accounting Standards Update 2014-09 \| Merck Sharp & Dohme Corp
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total interest of unearned revenue												7,100,000		7,100,000
Collaboration Agreement \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Up-front, nonrefundable and non-creditable payment received											$ 10,000,000
MDA Agreement \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Contingent payment received														1,500,000
Deferred revenue			1,700,000									0		0
Total revenue													$ 1,800,000		$ 5,400,000
Up-front, nonrefundable and non-creditable payment received										$ 10,000,000
Maximum amount eligible to receive for each product developed														52,500,000
Milestone Payment and New Supply Agreement \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue												1,500,000		3,000,000
Research and Development Services \| EMD Serono
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Total revenue												1,100,000		3,400,000
Supply Agreement \| SutroVax
Collaborative Arrangements And Noncollaborative Arrangement Transactions [Line Items]
Other revenue-related parties												800,000		1,100,000
Accounts receivable, related parties			$ 49,000									$ 800,000		$ 800,000