Preferred Stock, Common Stock and Stockholders' Equity - Warrants - Additional Information (Detail) - shares	12 Months Ended
Dec. 31, 2022	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Warrants to purchase shares of common stock expired	139,972
Issuance of common stock from warrant exercise	0
Warrants outstanding to purchase common stock		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