XML 45 R38.htm IDEA: XBRL DOCUMENT
v3.19.3

Related Party Transactions - Summary of Fees to Vornado (Detail) - Vornado - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Related Party Transaction [Line Items] |  |  |  |
Fees to related party | $ 3,361 | $ 1,742 | $ 9,980 | $ 5,116
Company management fees |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Fees to related party | 700 | 700 | 2,100 | 2,100
Development fees |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Fees to related party | 0 | 17 | 29 | 26
Leasing fees |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Fees to related party | 1,422 | 13 | 4,168 | 13
Property management, cleaning, engineering and security fees |  |  |  |
Related Party Transaction [Line Items] |  |  |  |
Fees to related party | $ 1,239 | $ 1,012 | $ 3,683 | $ 2,977

X
- Definition Expenses recognized resulting from transactions (excluding transactions that are eliminated in consolidated or combined financial statements) with related party. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 850 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=6457730&loc=d3e39549-107864 + Details
Name: | us-gaap_RelatedPartyTransactionExpensesFromTransactionsWithRelatedParty
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_RelatedPartyTransactionLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

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

X
- Details
Name: | us-gaap_RelatedPartyTransactionAxis=alx_CompanyManagementFeesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionAxis=alx_DevelopmentFeesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionAxis=alx_LeasingFeesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_RelatedPartyTransactionAxis=alx_PropertyManagementFeesMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |