v3.21.2

Common Stock Offering - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Thousands	1 Months Ended	3 Months Ended	9 Months Ended
	Feb. 28, 2021	Mar. 31, 2021	Sep. 30, 2021	Sep. 30, 2020
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Exercise of employee stock options, shares			208,259	117,854
Sale of common stock	1,872,574
Proceeds from common stock offerings, net of issuance costs	$ 95,725		$ 95,288	$ 27,699
Incurred expenses		$ 266
Equity Distribution Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Maximum offering capacity	$ 9,269
Canaccord Equity Distribution Agreement [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Sale of stock, consideration received on transaction				$ 25,000
Public Offering [Member]
Organization Consolidation And Presentation Of Financial Statements Disclosure [Line Items]
Issued and sale of common stock	1,666,667
Sale of stock, price per share	$ 54.00
Additional common stock shares issued	205,907
Underwriting discount and commission per share	$ 2.835
Exercise of employee stock options, shares	205,907

The cash inflow from the additional capital contribution to the entity.

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ExOne Co 10-Q