XML 22 R10.htm IDEA: XBRL DOCUMENT
v3.26.1

Consolidated Statements of Cash Flows (Unaudited) (Parenthetical) - USD ($) $ in Thousands | 6 Months Ended
--- | ---
Jun. 30, 2026 | Jun. 30, 2025
Development fees | $ 667 | $ 1,380
Vornado |  |
Development fees | $ 79 | $ 207

X
- Definition Non-cash additions to real estate included in accounts payable and accrued expenses. + References No definition available. + Details
Name: | alx_NonCashAdditionsToRealEstate
Namespace Prefix: | alx_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Details
Name: | us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_RelatedPartyMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |