XML 27 R12.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Rego Park II Loan Participation | 12 Months Ended
--- | ---
Dec. 31, 2017
Mortgage Loans on Real Estate [Abstract] |
Rego Park II Loan Participation | REGO PARK II LOAN PARTICIPATION On July 28, 2017, we entered into a participation and servicing agreement with the lender on our Rego Park II shopping center loan, which matures on November 30, 2018. We invested $200,000,000 to participate in the loan and are entitled to interest at LIBOR plus 1.60% (3.17% as of December 31, 2017). The investment is presented as “Rego Park II loan participation” on our consolidated balance sheet as of December 31, 2017 and interest earned is recognized as “interest and other income, net” in our consolidated statement of income for the year ended December 31, 2017.

X
- Definition Investment in loan participation. + References No definition available. + Details
Name: | alx_InvestmentInLoanParticipationTextBlock
Namespace Prefix: | alx_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_MortgageLoansOnRealEstateAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration