Summary of Significant Accounting Policies - Schedule of Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Accounting Policies [Abstract]
Net loss attributable to Silk Road Medical, Inc. common stockholders									$ (47,365)	$ (52,415)	$ (37,629)
Weighted average common stock outstanding used to compute net loss per share, basic and diluted (in shares)									32,965,539	22,956,679	960,882
Net loss per share, basic and diluted (in USD per share)	$ (0.49)	$ (0.31)	$ (0.32)	$ (0.32)	$ (0.27)	$ (0.26)	$ (0.42)	$ (20.12)	$ (1.44)	$ (2.28)	$ (39.16)