Stockholders' Equity - Warrants - Additional Information (Detail) - shares	3 Months Ended
Mar. 31, 2023	Dec. 31, 2022
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Warrants to purchase shares of common stock expired	138,972
Warrants outstanding to purchase common stock	0	0

Class of warrant or right number of securities expired.

No definition available.

Name:	evok_ClassOfWarrantOrRightNumberOfSecuritiesExpired
Namespace Prefix:	evok_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration