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Equity-Based Compensation - Narrative (Details) - USD ($) $ / shares in Units, $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Compensation cost not yet recognized	$ 4,767
Compensation expense recognition period	2 years 9 months 18 days
Weighted-average grant date fair value (in dollars per share)	$ 1.33	$ 1.96
Aggregate intrinsic value, stock options, exercised	$ 74	$ 13
Exicure, Inc. 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of additional shares authorized, potential maximum additional shares (in shares)	4,600,000
Number of additional shares authorized, percentage of common stock outstanding			5.00%
Number of shares available for grant (in shares)	2,219,311
Options to purchase common stock \| Exicure, Inc. 2017 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Number of shares available for grant (in shares)			4,303,463