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

Fair Value Measurements - Additional Information (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of equity securities	$ 37,181,000	$ 41,644,000
Unrealized (loss) gain on equity securities	(4,454,000)	41,498,000
Vaxcyte, Inc. \| Vaxcyte Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Estimated fair value of equity securities	37,200,000	41,600,000
Unrealized (loss) gain on equity securities	(4,500,000)	41,500,000
Vaxcyte, Inc. \| Vaxcyte Common Stock \| Payment Received for Option Exercises and Revaluation of Prior Preferred Stock Warrant Converted to Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Unrealized (loss) gain on equity securities	$ 9,000	$ 146,000
Vaxcyte, Inc. \| Equity Securities \| Vaxcyte Common Stock
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Number of shares held	1,562,879	1,567,324
Fair Value Measurements Recurring
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities held	$ 265,750,000	$ 366,617,000
Fair Value Measurements Recurring \| Level 3
Fair Value Assets And Liabilities Measured On Recurring And Nonrecurring Basis [Line Items]
Securities held	$ 0	$ 0