The Company and Liquidity	3 Months Ended
Mar. 31, 2024
Organization, Consolidation and Presentation of Financial Statements [Abstract]
The Company and Liquidity	1. The Company and Liquidity Alector, Inc. (Alector or the Company) is a Delaware corporation headquartered in South San Francisco, California. Alector is a clinical stage biotechnology company pioneering immuno-neurology, a novel therapeutic approach for the treatment of neurodegeneration. Public Offering On January 19, 2024, the Company completed a public offering through selling and issuing 10,869,566 shares of common stock at a price per share of $6.57, resulting in aggregate net proceeds of $71.1 million, after deducting underwriting discounts and commissions and offering costs.

The entire disclosure for organization, consolidation and basis of presentation of financial statements disclosure.

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480424/946-10-50-1

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 946
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480424/946-10-50-2

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 810
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//810/tableOfContent

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 205
-Name Accounting Standards Codification
-Publisher FASB
-URI https://asc.fasb.org//205/tableOfContent

Name:	us-gaap_OrganizationConsolidationAndPresentationOfFinancialStatementsDisclosureTextBlock
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:textBlockItemType
Balance Type:	na
Period Type:	duration