XML 155 R132.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Schedule III - Real Estate and Accumulated Depreciation (Details) - USD ($) $ in Thousands | Dec. 31, 2024 | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | --- | --- | ---
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | $ 1,947,474 |  |  |
Initial Cost |  |  |  |
Land | 1,504,523 |  |  |
Building & Improvements | 4,645,400 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | (147,482) |  |  |
Building & Improvements | 605,300 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 1,357,041 |  |  |
Building & Improvements | 5,250,700 |  |  |
Total | 6,607,741 | $ 6,102,864 | $ 9,198,799 | $ 7,650,907
Accumulated Depreciation | 2,126,081 | $ 1,968,004 | $ 2,039,554 | $ 1,896,199
420 Lexington Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 272,326 |  |  |
Initial Cost |  |  |  |
Land | 0 |  |  |
Building & Improvements | 333,499 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 79,607 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 0 |  |  |
Building & Improvements | 413,106 |  |  |
Total | 413,106 |  |  |
Accumulated Depreciation | 233,848 |  |  |
711 Third Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 19,844 |  |  |
Building & Improvements | 115,769 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 16,578 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 19,844 |  |  |
Building & Improvements | 132,347 |  |  |
Total | 152,191 |  |  |
Accumulated Depreciation | 84,768 |  |  |
555 W. 57th Street |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 18,846 |  |  |
Building & Improvements | 140,946 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 21,526 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 18,846 |  |  |
Building & Improvements | 162,472 |  |  |
Total | 181,318 |  |  |
Accumulated Depreciation | 103,967 |  |  |
461 Fifth Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 0 |  |  |
Building & Improvements | 88,276 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 28,873 |  |  |
Building & Improvements | 15,200 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 28,873 |  |  |
Building & Improvements | 103,476 |  |  |
Total | 132,349 |  |  |
Accumulated Depreciation | 49,460 |  |  |
750 Third Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 51,093 |  |  |
Building & Improvements | 251,523 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 114,773 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 51,093 |  |  |
Building & Improvements | 366,296 |  |  |
Total | 417,389 |  |  |
Accumulated Depreciation | 115,992 |  |  |
485 Lexington Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 450,000 |  |  |
Initial Cost |  |  |  |
Land | 78,282 |  |  |
Building & Improvements | 452,631 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | (4,635) |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 78,282 |  |  |
Building & Improvements | 447,996 |  |  |
Total | 526,278 |  |  |
Accumulated Depreciation | 217,606 |  |  |
810 Seventh Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 114,077 |  |  |
Building & Improvements | 550,819 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 13,809 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 114,077 |  |  |
Building & Improvements | 564,628 |  |  |
Total | 678,705 |  |  |
Accumulated Depreciation | 252,324 |  |  |
1185 Avenue of the Americas |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 0 |  |  |
Building & Improvements | 791,106 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 46,785 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 0 |  |  |
Building & Improvements | 837,891 |  |  |
Total | 837,891 |  |  |
Accumulated Depreciation | 418,159 |  |  |
1350 Avenue of the Americas |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 90,941 |  |  |
Building & Improvements | 431,517 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 26,318 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 90,941 |  |  |
Building & Improvements | 457,835 |  |  |
Total | 548,776 |  |  |
Accumulated Depreciation | 211,252 |  |  |
1-6 Landmark Square |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 100,000 |  |  |
Initial Cost |  |  |  |
Land | 27,852 |  |  |
Building & Improvements | 161,343 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | (6,939) |  |  |
Building & Improvements | (13,804) |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 20,913 |  |  |
Building & Improvements | 147,539 |  |  |
Total | 168,452 |  |  |
Accumulated Depreciation | 51,883 |  |  |
7 Landmark Square |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 1,721 |  |  |
Building & Improvements | 8,417 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | (1,338) |  |  |
Building & Improvements | (6,235) |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 383 |  |  |
Building & Improvements | 2,182 |  |  |
Total | 2,565 |  |  |
Accumulated Depreciation | 783 |  |  |
100 Church Street |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 370,000 |  |  |
Initial Cost |  |  |  |
Land | 34,994 |  |  |
Building & Improvements | 183,932 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 16,674 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 34,994 |  |  |
Building & Improvements | 200,606 |  |  |
Total | 235,600 |  |  |
Accumulated Depreciation | 84,431 |  |  |
125 Park Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 120,900 |  |  |
Building & Improvements | 270,598 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 30,032 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 120,900 |  |  |
Building & Improvements | 300,630 |  |  |
Total | 421,530 |  |  |
Accumulated Depreciation | 139,949 |  |  |
19 East 65th Street |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 8,603 |  |  |
Building & Improvements | 2,074 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 4,990 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 8,603 |  |  |
Building & Improvements | 7,064 |  |  |
Total | 15,667 |  |  |
Accumulated Depreciation | 10 |  |  |
304 Park Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 54,489 |  |  |
Building & Improvements | 90,643 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 12,056 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 54,489 |  |  |
Building & Improvements | 102,699 |  |  |
Total | 157,188 |  |  |
Accumulated Depreciation | 36,859 |  |  |
752-760 Madison Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 284,286 |  |  |
Building & Improvements | 8,314 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | (2,748) |  |  |
Building & Improvements | 165,708 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 281,538 |  |  |
Building & Improvements | 174,022 |  |  |
Total | 455,560 |  |  |
Accumulated Depreciation | 5,315 |  |  |
110 Greene Street |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 45,120 |  |  |
Building & Improvements | 228,393 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 4,741 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 45,120 |  |  |
Building & Improvements | 233,134 |  |  |
Total | 278,254 |  |  |
Accumulated Depreciation | 64,093 |  |  |
7 Dey / 185 Broadway |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 190,148 |  |  |
Initial Cost |  |  |  |
Land | 45,540 |  |  |
Building & Improvements | 27,865 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 209,670 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 45,540 |  |  |
Building & Improvements | 237,535 |  |  |
Total | 283,075 |  |  |
Accumulated Depreciation | 21,860 |  |  |
885 Third Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 138,444 |  |  |
Building & Improvements | 244,040 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | (138,444) |  |  |
Building & Improvements | (119,024) |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 0 |  |  |
Building & Improvements | 125,016 |  |  |
Total | 125,016 |  |  |
Accumulated Depreciation | 15,506 |  |  |
690 Madison Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 13,820 |  |  |
Building & Improvements | 51,732 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | (7,985) |  |  |
Building & Improvements | (27,336) |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 5,835 |  |  |
Building & Improvements | 24,396 |  |  |
Total | 30,231 |  |  |
Accumulated Depreciation | 5,132 |  |  |
100 Park Avenue |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 360,000 |  |  |
Initial Cost |  |  |  |
Land | 230,891 |  |  |
Building & Improvements | 133,269 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 0 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 230,891 |  |  |
Building & Improvements | 133,269 |  |  |
Total | 364,160 |  |  |
Accumulated Depreciation | 0 |  |  |
10 East 53rd Street |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 205,000 |  |  |
Initial Cost |  |  |  |
Land | 104,143 |  |  |
Building & Improvements | 62,470 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | 0 |  |  |
Building & Improvements | 0 |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 104,143 |  |  |
Building & Improvements | 62,470 |  |  |
Total | 166,613 |  |  |
Accumulated Depreciation | 4,710 |  |  |
Other |  |  |  |
SEC Schedule, 12-28, Real Estate Companies, Investment in Real Estate and Accumulated Depreciation [Line Items] |  |  |  |
Encumbrances | 0 |  |  |
Initial Cost |  |  |  |
Land | 20,637 |  |  |
Building & Improvements | 16,224 |  |  |
Cost Capitalized Subsequent To Acquisition |  |  |  |
Land | (18,901) |  |  |
Building & Improvements | (2,133) |  |  |
Gross Amount at Which Carried at Close of Period |  |  |  |
Land | 1,736 |  |  |
Building & Improvements | 14,091 |  |  |
Total | 15,827 |  |  |
Accumulated Depreciation | $ 8,174 |  |  |

X
- Definition -- None. No documentation exists for this element. -- + References No definition available. + Details
Name: | slg_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionAbstract
Namespace Prefix: | slg_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Represents the carrying amount as of the balance sheet date of building and improvement costs that were capitalized after acquisition. + References No definition available. + Details
Name: | slg_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionOfBuildingAndImprovements
Namespace Prefix: | slg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Represents the carrying amount as of the balance sheet date of land costs that were capitalized after acquisition. + References No definition available. + Details
Name: | slg_RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionOfLand
Namespace Prefix: | slg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of lien or mortgage outstanding on real estate investment properties for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column B -Publisher SEC Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column B)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 + Details
Name: | srt_RealEstateAndAccumulatedDepreciationAmountOfEncumbrances
Namespace Prefix: | srt_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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 Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column A -Footnote 2 -Publisher SEC Reference 2: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column I -Publisher SEC Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column H -Publisher SEC Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column G -Publisher SEC Reference 5: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column F -Publisher SEC Reference 6: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column E -Publisher SEC Reference 7: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column D -Publisher SEC Reference 8: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column C -Publisher SEC Reference 9: http://www.xbrl.org/2003/role/disclosureRef -Name Regulation S-X (SX) -Number 210 -Section 12 -Subsection 28 -Paragraph Column B -Publisher SEC Reference 10: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column F)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 Reference 11: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column E)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 Reference 12: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column D)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 Reference 13: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column C)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 Reference 14: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column I)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 Reference 15: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column A)(Footnote 2)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 Reference 16: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column B)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 Reference 17: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column G)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 Reference 18: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column H)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 + Details
Name: | srt_RealEstateAndAccumulatedDepreciationLineItems
Namespace Prefix: | srt_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Amount of accumulated depreciation pertaining to real estate investments for entities with a substantial portion of business acquiring and holding investment real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column F)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 + Details
Name: | us-gaap_RealEstateAccumulatedDepreciation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount before accumulated depreciation of buildings and improvements for entities with a substantial portion of business acquiring and holding investment real estate. Excludes real estate not held as an investment or interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column E)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 + Details
Name: | us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of land for entities with a substantial portion of business acquiring and holding investment real estate. Excludes real estate not held as an investment or interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column E)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 + Details
Name: | us-gaap_RealEstateAndAccumulatedDepreciationCarryingAmountOfLand
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

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

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

X
- Definition Initial cost of buildings and improvements for entities with a substantial portion of business acquiring and holding investment real estate. Excludes real estate not held as an investment or interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column C)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 + Details
Name: | us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Initial cost of land for entities with a substantial portion of business acquiring and holding investment real estate. Excludes real estate not held as an investment or interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column C)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 + Details
Name: | us-gaap_RealEstateAndAccumulatedDepreciationInitialCostOfLand
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount, before accumulated depreciation, of real estate investment by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate. Excludes real estate not held as investment or interest. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 970 -SubTopic 360 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-28(Column E)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1 + Details
Name: | us-gaap_RealEstateGrossAtCarryingValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_LexingtonAvenue420Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_ThirdAvenue711Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_W57Street555Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_FifthAvenue461Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_ThirdAvenue750Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_LexingtonAvenue485Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_SeventhAvenue810Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_AvenueOfTheAmericas1185Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_AvenueOfTheAmericas1350Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_LandmarkSquare1To6Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_LandmarkSquare7Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_ChurchStreet100Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_ParkAvenue125Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_A19East65thStreetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_ParkAvenue304Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_A752760MadisonAvenueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_A110GreeneStreetMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_A7Dey185BroadwayMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_ThirdAvenue885Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_A690MadisonAvenueMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_ParkAvenue100Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_East53rdStreet10Member
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_OtherPropertyInvestmentsMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |