XML 43 R27.htm IDEA: XBRL DOCUMENT
v3.20.4

Summary of Significant Accounting Policies (Tables) | 12 Months Ended
--- | ---
Dec. 31, 2020
Accounting Policies [Abstract] |
Reconciliation Of Net Income Attributable To Common Stockholders To Estimated Taxable Income | The following table reconciles our net income to estimated taxable income for the years ended December 31, 2020, 2019 and 2018.
(Unaudited and in thousands) | Year Ended December 31,
| 2020 |  | 2019 |  | 2018
Net income | $ | 41,939 |  |  | $ | 60,075 |  |  | $ | 32,844 |
Straight-line rent adjustments | 21,048 |  |  | 2,359 |  |  | 5,870 |
Depreciation and amortization | 2,112 |  |  | 2,751 |  |  | (6,586) |
Change in fair value of marketable securities (see Note 6) | 8,599 |  |  | 8,757 |  |  | 11,990 |
Loss from discontinued operations (see Note 7) | — |  |  | — |  |  | 23,797 |
Other | 7,677 |  |  | 137 |  |  | 440 |
Estimated taxable income | $ | 81,375 |  |  | $ | 74,079 |  |  | $ | 68,355 |

X
- Definition Table reconciling net income attributable to common stockholders to estimated taxable income + References No definition available. + Details
Name: | alx_ReconciliationOfNetIncomeAttributableToCommonShareholdersToEstimatedTaxableIncomeTableTextBlock
Namespace Prefix: | alx_
Data Type: | nonnum:textBlockItemType
Balance Type: | na
Period Type: | duration

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