$SLG
SL Green Realty Corp Stock $slg

$slg Overview Financials Valuation SEC Filings Company Website

2019 Q4 Form 10-K Financial Statement

#000104097121000007 Filed on February 26, 2021

Income Statement

Concept	2019 Q4	2018 Q4	2018
Revenue	$308.1M	$317.0M	$1.227B
YoY Change	-2.82%	-12.26%	-18.79%
Cost Of Revenue	$114.9M	$109.3M	$448.7M
YoY Change	5.12%	-21.08%	-21.4%
Gross Profit	$193.2M	$207.7M	$778.7M
YoY Change	-6.98%	-6.78%	-17.21%
Gross Profit Margin	62.71%	65.51%	63.44%
Selling, General & Admin	$25.90M	$26.50M	$92.60M
YoY Change	-2.26%	2.32%	-7.86%
% of Gross Profit	13.41%	12.76%	11.89%
Research & Development
YoY Change
% of Gross Profit
Depreciation & Amortization	$67.20M	$74.10M	$289.9M
YoY Change	-9.31%	-16.46%	-30.78%
% of Gross Profit	34.78%	35.68%	37.23%
Operating Expenses	$90.00M	$103.7M	$92.60M
YoY Change	-13.21%	-6.07%	-7.86%
Operating Profit	$103.2M	$104.0M	$686.1M
YoY Change	-0.77%	-7.47%	-18.33%
Interest Expense	-$59.70M	$110.4M	$236.7M
YoY Change	-154.08%	-292.33%	-7.91%
% of Operating Profit	-57.85%	106.15%	34.5%
Other Income/Expense, Net	$0.00	-$220.9M	-$227.5M
YoY Change	-100.0%	137.02%	27.45%
Pretax Income	$24.30M	-$58.30M	$270.9M
YoY Change	-141.68%	-223.43%	64.15%
Income Tax			$2.800M
% Of Pretax Income			1.03%
Net Earnings	$21.17M	-$57.48M	$247.3M
YoY Change	-136.83%	-281.22%	143.91%
Net Earnings / Revenue	6.87%	-18.13%	20.15%
Basic Earnings Per Share	$0.21	-$0.73	$2.75
Diluted Earnings Per Share	$0.21	-$0.73	$2.75
COMMON SHARES
Basic Shares Outstanding	80.11M shares	85.27M shares	84.09M shares
Diluted Shares Outstanding			89.07M shares

Balance Sheet

Concept	2019 Q4	2018 Q4	2018
SHORT-TERM ASSETS
Cash & Short-Term Investments	$196.0M	$158.1M	$129.0M
YoY Change	23.93%	1.05%	0.78%
Cash & Equivalents	$166.1M	$129.5M	$129.0M
Short-Term Investments	$29.89M	$28.64M
Other Short-Term Assets
YoY Change
Inventory	$392.0M
Prepaid Expenses
Receivables	$348.0M	$406.0M	$406.0M
Other Receivables	$0.00	$0.00	$0.00
Total Short-Term Assets	$906.0M	$535.0M	$535.0M
YoY Change	69.35%	-41.34%	-41.34%
LONG-TERM ASSETS
Property, Plant & Equipment	$6.724B	$6.415B	$6.415B
YoY Change	4.82%	-18.86%	-18.86%
Goodwill
YoY Change
Intangibles
YoY Change
Long-Term Investments	$2.913B	$3.019B	$5.147B
YoY Change	-3.52%	27.76%	14.23%
Other Assets	$281.0M	$359.0M	$359.0M
YoY Change	-21.73%	3.16%	3.16%
Total Long-Term Assets	$11.86B	$12.22B	$12.22B
YoY Change	-2.91%	-6.54%	-6.54%
TOTAL ASSETS
Total Short-Term Assets	$906.0M	$535.0M	$535.0M
Total Long-Term Assets	$11.86B	$12.22B	$12.22B
Total Assets	$12.77B	$12.75B	$12.75B
YoY Change	0.12%	-8.81%	-8.81%
SHORT-TERM LIABILITIES
YoY Change
Accounts Payable	$167.0M	$147.0M	$147.0M
YoY Change	13.61%	7.3%	7.3%
Accrued Expenses	$404.0M	$27.00M	$27.00M
YoY Change	1396.3%	-28.95%	-28.95%
Deferred Revenue
YoY Change
Short-Term Debt	$0.00	$0.00	$0.00
YoY Change
Long-Term Debt Due
YoY Change
Total Short-Term Liabilities	$713.0M	$319.0M	$319.0M
YoY Change	123.51%	-3.63%	-3.63%
LONG-TERM LIABILITIES
Long-Term Debt	$5.553B	$5.585B	$5.585B
YoY Change	-0.57%	-5.31%	-5.31%
Other Long-Term Liabilities	$291.0M	$211.0M	$211.0M
YoY Change	37.91%	-47.25%	-47.25%
Total Long-Term Liabilities	$5.844B	$5.796B	$5.796B
YoY Change	0.83%	-7.97%	-7.97%
TOTAL LIABILITIES
Total Short-Term Liabilities	$713.0M	$319.0M	$319.0M
Total Long-Term Liabilities	$5.844B	$5.796B	$5.796B
Total Liabilities	$6.556B	$6.115B	$6.549B
YoY Change	7.21%	-7.76%	-12.16%
SHAREHOLDERS EQUITY
Retained Earnings	$1.085B	$1.279B
YoY Change	-15.19%	12.26%
Common Stock	$803.0K	$847.0K
YoY Change	-5.19%	-9.8%
Preferred Stock
YoY Change
Treasury Stock (at cost)	$124.0M	$124.0M
YoY Change	0.0%	0.0%
Treasury Stock Shares	1.026M shares	1.055M shares
Shareholders Equity	$5.441B	$5.902B	$6.202B
YoY Change
Total Liabilities & Shareholders Equity	$12.77B	$12.75B	$12.75B
YoY Change	0.12%	-8.81%	-8.81%

Cashflow Statement

Concept	2019 Q4	2018 Q4	2018
OPERATING ACTIVITIES
Net Income	$21.17M	-$57.48M	$247.3M
YoY Change	-136.83%	-281.22%	143.91%
Depreciation, Depletion And Amortization	$67.20M	$74.10M	$289.9M
YoY Change	-9.31%	-16.46%	-30.78%
Cash From Operating Activities	$77.10M	$124.0M	$441.5M
YoY Change	-37.82%	-5.13%	-18.69%
INVESTING ACTIVITIES
Capital Expenditures	-$103.3M	-$110.9M	$254.5M
YoY Change	-6.85%	26.45%	-24.27%
Acquisitions
YoY Change
Other Investing Activities	$458.7M	$292.3M	$996.6M
YoY Change	56.93%	57.83%	157.72%
Cash From Investing Activities	$355.4M	$181.5M	$681.7M
YoY Change	95.81%	85.96%	2996.49%
FINANCING ACTIVITIES
Cash Dividend Paid			$313.2M
YoY Change			-6.09%
Common Stock Issuance & Retirement, Net			$979.5M
YoY Change			21.49%
Debt Paid & Issued, Net
YoY Change
Cash From Financing Activities	-407.6M	-284.9M	-$1.094B
YoY Change	43.07%	-13.03%	59.73%
NET CHANGE
Cash From Operating Activities	77.10M	124.0M	$441.5M
Cash From Investing Activities	355.4M	181.5M	$681.7M
Cash From Financing Activities	-407.6M	-284.9M	-$1.094B
Net Change In Cash	24.90M	20.60M	$29.09M
YoY Change	20.87%	-120.75%	-124.25%
FREE CASH FLOW
Cash From Operating Activities	$77.10M	$124.0M	$441.5M
Capital Expenditures	-$103.3M	-$110.9M	$254.5M
Free Cash Flow	$180.4M	$234.9M	$187.1M
YoY Change	-23.2%	7.55%	-9.62%

Facts In Submission

Frame	Concept Type	Concept / XBRL Key	Value	Unit
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CY2020	dei	Document Period End Date DocumentPeriodEndDate	2020-12-31
CY2020	dei	Current Fiscal Year End Date CurrentFiscalYearEndDate	--12-31
CY2020	dei	Document Transition Report DocumentTransitionReport	false
CY2020	dei	Entity File Number EntityFileNumber	1-13199
CY2020	dei	Entity Registrant Name EntityRegistrantName	SL GREEN REALTY CORP
CY2020	dei	Entity Incorporation State Country Code EntityIncorporationStateCountryCode	MD
CY2020	dei	Entity Tax Identification Number EntityTaxIdentificationNumber	13-3956775
CY2020	dei	Entity Address Address Line1 EntityAddressAddressLine1	420 Lexington Avenue
CY2020	dei	Entity Address City Or Town EntityAddressCityOrTown	New York
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CY2019	us-gaap	Depreciation And Amortization DepreciationAndAmortization	272358000	USD
CY2018	us-gaap	Depreciation And Amortization DepreciationAndAmortization	279507000	USD
CY2020	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	35298000	USD
CY2019	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	0	USD
CY2018	us-gaap	Provision For Loan And Lease Losses ProvisionForLoanAndLeaseLosses	6839000	USD
CY2020	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	503000	USD
CY2019	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	729000	USD
CY2018	us-gaap	Other Cost And Expense Operating OtherCostAndExpenseOperating	1099000	USD
CY2020	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	91826000	USD
CY2019	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	100875000	USD
CY2018	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	92631000	USD
CY2020	slg	Total Costs And Expenses Including Nonoperating Income Expense TotalCostsAndExpensesIncludingNonoperatingIncomeExpense	958326000	USD
CY2019	slg	Total Costs And Expenses Including Nonoperating Income Expense TotalCostsAndExpensesIncludingNonoperatingIncomeExpense	1034764000	USD
CY2018	slg	Total Costs And Expenses Including Nonoperating Income Expense TotalCostsAndExpensesIncludingNonoperatingIncomeExpense	1049816000	USD
CY2020	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-25195000	USD
CY2019	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-34518000	USD
CY2018	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	7311000	USD
CY2020	us-gaap	Equity Method Investment Realized Gain Loss On Disposal EquityMethodInvestmentRealizedGainLossOnDisposal	2961000	USD
CY2019	us-gaap	Equity Method Investment Realized Gain Loss On Disposal EquityMethodInvestmentRealizedGainLossOnDisposal	76181000	USD
CY2018	us-gaap	Equity Method Investment Realized Gain Loss On Disposal EquityMethodInvestmentRealizedGainLossOnDisposal	303967000	USD
CY2020	slg	Purchase Price Fair Value Adjustment Gross PurchasePriceFairValueAdjustmentGross	187522000	USD
CY2019	slg	Purchase Price Fair Value Adjustment Gross PurchasePriceFairValueAdjustmentGross	69389000	USD
CY2020	slg	Depreciable Real Estate Reserves Effecton Earnings DepreciableRealEstateReservesEffectonEarnings	-60454000	USD
CY2019	slg	Depreciable Real Estate Reserves Effecton Earnings DepreciableRealEstateReservesEffectonEarnings	-7047000	USD
CY2018	slg	Depreciable Real Estate Reserves Effecton Earnings DepreciableRealEstateReservesEffectonEarnings	-227543000	USD
CY2018	slg	Purchase Price Fair Value Adjustment Gross PurchasePriceFairValueAdjustmentGross	57385000	USD
CY2020	us-gaap	Gains Losses On Sales Of Investment Real Estate GainsLossesOnSalesOfInvestmentRealEstate	215506000	USD
CY2019	us-gaap	Gains Losses On Sales Of Investment Real Estate GainsLossesOnSalesOfInvestmentRealEstate	-16749000	USD
CY2018	us-gaap	Gains Losses On Sales Of Investment Real Estate GainsLossesOnSalesOfInvestmentRealEstate	-30757000	USD
CY2020	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-17083000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	414758000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	291487000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	270856000	USD
CY2020	us-gaap	Noncontrolling Interest In Net Income Loss Operating Partnerships Redeemable NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable	20016000	USD
CY2019	us-gaap	Noncontrolling Interest In Net Income Loss Operating Partnerships Redeemable NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable	13301000	USD
CY2018	us-gaap	Noncontrolling Interest In Net Income Loss Operating Partnerships Redeemable NoncontrollingInterestInNetIncomeLossOperatingPartnershipsRedeemable	12216000	USD
CY2019	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	3.20
CY2020	us-gaap	Noncontrolling Interest In Net Income Loss Other Noncontrolling Interests Redeemable NoncontrollingInterestInNetIncomeLossOtherNoncontrollingInterestsRedeemable	14940000	USD
CY2019	us-gaap	Noncontrolling Interest In Net Income Loss Other Noncontrolling Interests Redeemable NoncontrollingInterestInNetIncomeLossOtherNoncontrollingInterestsRedeemable	-3159000	USD
CY2018	us-gaap	Noncontrolling Interest In Net Income Loss Other Noncontrolling Interests Redeemable NoncontrollingInterestInNetIncomeLossOtherNoncontrollingInterestsRedeemable	-6000	USD
CY2020	us-gaap	Noncontrolling Interest In Net Income Loss Preferred Unit Holders Redeemable NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable	8747000	USD
CY2019	us-gaap	Noncontrolling Interest In Net Income Loss Preferred Unit Holders Redeemable NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable	10911000	USD
CY2018	us-gaap	Noncontrolling Interest In Net Income Loss Preferred Unit Holders Redeemable NoncontrollingInterestInNetIncomeLossPreferredUnitHoldersRedeemable	11384000	USD
CY2020	us-gaap	Net Income Loss NetIncomeLoss	371055000	USD
CY2019	us-gaap	Net Income Loss NetIncomeLoss	270434000	USD
CY2018	us-gaap	Net Income Loss NetIncomeLoss	247262000	USD
CY2020	us-gaap	Dividends Preferred Stock DividendsPreferredStock	14950000	USD
CY2019	us-gaap	Dividends Preferred Stock DividendsPreferredStock	14950000	USD
CY2018	us-gaap	Dividends Preferred Stock DividendsPreferredStock	14950000	USD
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	356105000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	255484000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	232312000	USD
CY2020	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	4.88
CY2018	us-gaap	Earnings Per Share Basic EarningsPerShareBasic	2.75
CY2020	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	4.87
CY2019	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	3.19
CY2018	us-gaap	Earnings Per Share Diluted EarningsPerShareDiluted	2.75
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	72552000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	79415000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	84090000	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	77243000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	84234000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	89071000	shares
CY2020	us-gaap	Profit Loss ProfitLoss	414758000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	291487000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	270856000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-39743000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-47118000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss After Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossAfterReclassificationAndTax	-3622000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	-1318000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	1249000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Available For Sale Securities Adjustment Net Of Tax OtherComprehensiveIncomeLossAvailableForSaleSecuritiesAdjustmentNetOfTax	60000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-41061000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-45869000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax OtherComprehensiveIncomeLossNetOfTax	-3562000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	373697000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	245618000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax Including Portion Attributable To Noncontrolling Interest ComprehensiveIncomeNetOfTaxIncludingPortionAttributableToNoncontrollingInterest	267294000	USD
CY2020	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	43703000	USD
CY2019	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	21053000	USD
CY2018	us-gaap	Net Income Loss Attributable To Noncontrolling Interest NetIncomeLossAttributableToNoncontrollingInterest	23594000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-2299000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-2276000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Noncontrolling Interest OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToNoncontrollingInterest	-66000	USD
CY2020	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	332293000	USD
CY2019	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	226841000	USD
CY2018	us-gaap	Comprehensive Income Net Of Tax ComprehensiveIncomeNetOfTax	243766000	USD
CY2017Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	6589454000	USD
CY2018	slg	Profit Loss Less Minority Interest In Net Income Loss Operating Partnerships ProfitLossLessMinorityInterestInNetIncomeLossOperatingPartnerships	247256000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-3496000	USD
CY2018	us-gaap	Dividends Preferred Stock DividendsPreferredStock	14950000	USD
CY2018	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	136000	USD
CY2018	us-gaap	Stock Issued During Period Value Conversion Of Units StockIssuedDuringPeriodValueConversionOfUnits	16303000	USD
CY2018	slg	Reallocationof Noncontrolling Interest In Operating Partnership Increase Decrease ReallocationofNoncontrollingInterestInOperatingPartnershipIncreaseDecrease	34236000	USD
CY2018	slg	Deferred Compensation Plan And Stock Award Net DeferredCompensationPlanAndStockAwardNet	17484000	USD
CY2018	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	937795000	USD
CY2018	us-gaap	Stock Issued During Period Value Stock Options Exercised StockIssuedDuringPeriodValueStockOptionsExercised	28912000	USD
CY2018	slg	Consolidation Of Joint Venture Interest ConsolidationOfJointVentureInterest	5459000	USD
CY2018	us-gaap	Noncontrolling Interest Decrease From Deconsolidation NoncontrollingInterestDecreaseFromDeconsolidation	315116000	USD
CY2018	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	8364000	USD
CY2018	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	3.3834
CY2018	us-gaap	Dividends Common Stock DividendsCommonStock	282188000	USD
CY2018Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	5947855000	USD
CY2019	slg	Profit Loss Less Minority Interest In Net Income Loss Operating Partnerships ProfitLossLessMinorityInterestInNetIncomeLossOperatingPartnerships	267275000	USD
CY2019	us-gaap	Minority Interest Decrease From Redemptions MinorityInterestDecreaseFromRedemptions	25845000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-43593000	USD
CY2019	us-gaap	Dividends Preferred Stock DividendsPreferredStock	14950000	USD
CY2019	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	334000	USD
CY2019	us-gaap	Stock Issued During Period Value Conversion Of Units StockIssuedDuringPeriodValueConversionOfUnits	471000	USD
CY2019	slg	Reallocationof Noncontrolling Interest In Operating Partnership Increase Decrease ReallocationofNoncontrollingInterestInOperatingPartnershipIncreaseDecrease	-34320000	USD
CY2019	slg	Deferred Compensation Plan And Stock Award Net DeferredCompensationPlanAndStockAwardNet	25763000	USD
CY2019	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	384399000	USD
CY2019	slg	Consolidation Of Joint Venture Interest ConsolidationOfJointVentureInterest	58462000	USD
CY2019	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	478000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	3.5352
CY2019	us-gaap	Dividends Common Stock DividendsCommonStock	279377000	USD
CY2019Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	5517198000	USD
CY2020	slg	Profit Loss Less Minority Interest In Net Income Loss Operating Partnerships ProfitLossLessMinorityInterestInNetIncomeLossOperatingPartnerships	385995000	USD
CY2020	us-gaap	Minority Interest Decrease From Redemptions MinorityInterestDecreaseFromRedemptions	1536000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Net Of Tax Portion Attributable To Parent OtherComprehensiveIncomeLossNetOfTaxPortionAttributableToParent	-38762000	USD
CY2020	us-gaap	Dividends Preferred Stock DividendsPreferredStock	14950000	USD
CY2020	us-gaap	Stock Issued During Period Value Dividend Reinvestment Plan StockIssuedDuringPeriodValueDividendReinvestmentPlan	1006000	USD
CY2020	us-gaap	Stock Issued During Period Value Conversion Of Units StockIssuedDuringPeriodValueConversionOfUnits	8744000	USD
CY2020	slg	Reallocationof Noncontrolling Interest In Operating Partnership Increase Decrease ReallocationofNoncontrollingInterestInOperatingPartnershipIncreaseDecrease	32598000	USD
CY2020	slg	Deferred Compensation Plan And Stock Award Net DeferredCompensationPlanAndStockAwardNet	25271000	USD
CY2020	us-gaap	Treasury Stock Value Acquired Cost Method TreasuryStockValueAcquiredCostMethod	532262000	USD
CY2020	slg	Consolidation Of Joint Venture Interest ConsolidationOfJointVentureInterest	12477000	USD
CY2020	us-gaap	Minority Interest Decrease From Distributions To Noncontrolling Interest Holders MinorityInterestDecreaseFromDistributionsToNoncontrollingInterestHolders	78855000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	4.7908
CY2020	us-gaap	Dividends Common Stock DividendsCommonStock	341945000	USD
CY2020Q4	us-gaap	Stockholders Equity Including Portion Attributable To Noncontrolling Interest StockholdersEquityIncludingPortionAttributableToNoncontrollingInterest	4935795000	USD
CY2020	us-gaap	Profit Loss ProfitLoss	414758000	USD
CY2019	us-gaap	Profit Loss ProfitLoss	291487000	USD
CY2018	us-gaap	Profit Loss ProfitLoss	270856000	USD
CY2020	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	325462000	USD
CY2019	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	284011000	USD
CY2018	us-gaap	Depreciation Depletion And Amortization DepreciationDepletionAndAmortization	289899000	USD
CY2020	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-25195000	USD
CY2019	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	-34518000	USD
CY2018	us-gaap	Income Loss From Equity Method Investments IncomeLossFromEquityMethodInvestments	7311000	USD
CY2020	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	679000	USD
CY2019	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	864000	USD
CY2018	us-gaap	Equity Method Investment Dividends Or Distributions EquityMethodInvestmentDividendsOrDistributions	10277000	USD
CY2020	us-gaap	Equity Method Investment Realized Gain Loss On Disposal EquityMethodInvestmentRealizedGainLossOnDisposal	2961000	USD
CY2019	us-gaap	Equity Method Investment Realized Gain Loss On Disposal EquityMethodInvestmentRealizedGainLossOnDisposal	76181000	USD
CY2018	us-gaap	Equity Method Investment Realized Gain Loss On Disposal EquityMethodInvestmentRealizedGainLossOnDisposal	303967000	USD
CY2020	slg	Purchase Price Fair Value Adjustment Gain Loss PurchasePriceFairValueAdjustmentGainLoss	187522000	USD
CY2019	slg	Purchase Price Fair Value Adjustment Gain Loss PurchasePriceFairValueAdjustmentGainLoss	69389000	USD
CY2018	slg	Purchase Price Fair Value Adjustment Gain Loss PurchasePriceFairValueAdjustmentGainLoss	57385000	USD
CY2020	slg	Depreciable Real Estate Reserves Cash Flow Effect DepreciableRealEstateReservesCashFlowEffect	-60454000	USD
CY2019	us-gaap	Gains Losses On Sales Of Investment Real Estate GainsLossesOnSalesOfInvestmentRealEstate	-16749000	USD
CY2018	us-gaap	Gains Losses On Sales Of Investment Real Estate GainsLossesOnSalesOfInvestmentRealEstate	-30757000	USD
CY2019	slg	Depreciable Real Estate Reserves Cash Flow Effect DepreciableRealEstateReservesCashFlowEffect	-7047000	USD
CY2018	slg	Depreciable Real Estate Reserves Cash Flow Effect DepreciableRealEstateReservesCashFlowEffect	-227543000	USD
CY2020	us-gaap	Gains Losses On Sales Of Investment Real Estate GainsLossesOnSalesOfInvestmentRealEstate	215506000	USD
CY2020	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	35298000	USD
CY2019	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	0	USD
CY2018	us-gaap	Provision For Loan Lease And Other Losses ProvisionForLoanLeaseAndOtherLosses	6839000	USD
CY2020	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2019	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	0	USD
CY2018	us-gaap	Gains Losses On Extinguishment Of Debt GainsLossesOnExtinguishmentOfDebt	-17083000	USD
CY2020	us-gaap	Straight Line Rent StraightLineRent	7582000	USD
CY2019	us-gaap	Straight Line Rent StraightLineRent	13941000	USD
CY2018	us-gaap	Straight Line Rent StraightLineRent	18216000	USD
CY2020	slg	Non Cash Lease Expense NonCashLeaseExpense	11984000	USD
CY2019	slg	Non Cash Lease Expense NonCashLeaseExpense	13744000	USD
CY2018	slg	Non Cash Lease Expense NonCashLeaseExpense	2016000	USD
CY2020	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-15178000	USD
CY2019	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-271000	USD
CY2018	us-gaap	Other Noncash Income Expense OtherNoncashIncomeExpense	-2932000	USD
CY2020	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	17074000	USD
CY2019	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	4968000	USD
CY2018	us-gaap	Increase Decrease In Accounts Receivable IncreaseDecreaseInAccountsReceivable	-6968000	USD
CY2020	us-gaap	Increase Decrease In Due From Related Parties Current IncreaseDecreaseInDueFromRelatedPartiesCurrent	-1451000	USD
CY2019	us-gaap	Increase Decrease In Due From Related Parties Current IncreaseDecreaseInDueFromRelatedPartiesCurrent	-7802000	USD
CY2018	us-gaap	Increase Decrease In Due From Related Parties Current IncreaseDecreaseInDueFromRelatedPartiesCurrent	1044000	USD
CY2020	us-gaap	Increase Decrease In Deferred Leasing Fees IncreaseDecreaseInDeferredLeasingFees	20900000	USD
CY2019	us-gaap	Increase Decrease In Deferred Leasing Fees IncreaseDecreaseInDeferredLeasingFees	70938000	USD
CY2018	us-gaap	Increase Decrease In Deferred Leasing Fees IncreaseDecreaseInDeferredLeasingFees	44158000	USD
CY2020	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	26137000	USD
CY2019	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	18630000	USD
CY2018	us-gaap	Increase Decrease In Other Operating Assets IncreaseDecreaseInOtherOperatingAssets	8310000	USD
CY2020	slg	Increase Decrease In Accrued Liabilities And Other IncreaseDecreaseInAccruedLiabilitiesAndOther	132171000	USD
CY2019	slg	Increase Decrease In Accrued Liabilities And Other IncreaseDecreaseInAccruedLiabilitiesAndOther	-25597000	USD
CY2018	slg	Increase Decrease In Accrued Liabilities And Other IncreaseDecreaseInAccruedLiabilitiesAndOther	4410000	USD
CY2020	us-gaap	Increase Decrease In Deferred Liabilities IncreaseDecreaseInDeferredLiabilities	20657000	USD
CY2019	us-gaap	Increase Decrease In Deferred Liabilities IncreaseDecreaseInDeferredLiabilities	10824000	USD
CY2018	us-gaap	Increase Decrease In Deferred Liabilities IncreaseDecreaseInDeferredLiabilities	12348000	USD
CY2020	slg	Increase Decrease In Operating Lease Liability IncreaseDecreaseInOperatingLeaseLiability	-11369000	USD
CY2019	slg	Increase Decrease In Operating Lease Liability IncreaseDecreaseInOperatingLeaseLiability	-11200000	USD
CY2018	slg	Increase Decrease In Operating Lease Liability IncreaseDecreaseInOperatingLeaseLiability	0	USD
CY2020	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	554236000	USD
CY2019	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	376473000	USD
CY2018	us-gaap	Net Cash Provided By Used In Operating Activities NetCashProvidedByUsedInOperatingActivities	441537000	USD
CY2020	us-gaap	Payments To Acquire Commercial Real Estate PaymentsToAcquireCommercialRealEstate	86846000	USD
CY2019	us-gaap	Payments To Acquire Commercial Real Estate PaymentsToAcquireCommercialRealEstate	262591000	USD
CY2018	us-gaap	Payments To Acquire Commercial Real Estate PaymentsToAcquireCommercialRealEstate	60486000	USD
CY2020	slg	Payments To Acquire Land Buildings And Improvements PaymentsToAcquireLandBuildingsAndImprovements	458140000	USD
CY2019	slg	Payments To Acquire Land Buildings And Improvements PaymentsToAcquireLandBuildingsAndImprovements	252986000	USD
CY2018	slg	Payments To Acquire Land Buildings And Improvements PaymentsToAcquireLandBuildingsAndImprovements	254460000	USD
CY2020	slg	Payments For Acquisition Deposits And Deferred Purchase Price PaymentsForAcquisitionDepositsAndDeferredPurchasePrice	0	USD
CY2019	slg	Payments For Acquisition Deposits And Deferred Purchase Price PaymentsForAcquisitionDepositsAndDeferredPurchasePrice	5239000	USD
CY2018	slg	Payments For Acquisition Deposits And Deferred Purchase Price PaymentsForAcquisitionDepositsAndDeferredPurchasePrice	0	USD
CY2020	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	70315000	USD
CY2019	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	128682000	USD
CY2018	us-gaap	Payments To Acquire Equity Method Investments PaymentsToAcquireEquityMethodInvestments	400429000	USD
CY2020	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	124572000	USD
CY2019	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	79020000	USD
CY2018	us-gaap	Proceeds From Equity Method Investment Dividends Or Distributions Return Of Capital ProceedsFromEquityMethodInvestmentDividendsOrDistributionsReturnOfCapital	233118000	USD
CY2020	us-gaap	Proceeds From Real Estate And Real Estate Joint Ventures ProceedsFromRealEstateAndRealEstateJointVentures	1112382000	USD
CY2019	us-gaap	Proceeds From Real Estate And Real Estate Joint Ventures ProceedsFromRealEstateAndRealEstateJointVentures	208302000	USD
CY2018	us-gaap	Proceeds From Real Estate And Real Estate Joint Ventures ProceedsFromRealEstateAndRealEstateJointVentures	1231004000	USD
CY2020	slg	Payments For Proceeds From Other Investments PaymentsForProceedsFromOtherInvestments	-32479000	USD
CY2019	slg	Payments For Proceeds From Other Investments PaymentsForProceedsFromOtherInvestments	7869000	USD
CY2018	slg	Payments For Proceeds From Other Investments PaymentsForProceedsFromOtherInvestments	38912000	USD
CY2020	slg	Origination Of Debt And Preferred Equity Investments OriginationOfDebtAndPreferredEquityInvestments	360953000	USD
CY2019	slg	Origination Of Debt And Preferred Equity Investments OriginationOfDebtAndPreferredEquityInvestments	607844000	USD
CY2018	slg	Origination Of Debt And Preferred Equity Investments OriginationOfDebtAndPreferredEquityInvestments	731216000	USD
CY2020	slg	Repayments Or Redemption Of Debt And Preferred Equity Investments RepaymentsOrRedemptionOfDebtAndPreferredEquityInvestments	763251000	USD
CY2019	slg	Repayments Or Redemption Of Debt And Preferred Equity Investments RepaymentsOrRedemptionOfDebtAndPreferredEquityInvestments	1092383000	USD
CY2018	slg	Repayments Or Redemption Of Debt And Preferred Equity Investments RepaymentsOrRedemptionOfDebtAndPreferredEquityInvestments	703043000	USD
CY2020	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	1056430000	USD
CY2019	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	114494000	USD
CY2018	us-gaap	Net Cash Provided By Used In Investing Activities NetCashProvidedByUsedInInvestingActivities	681662000	USD
CY2020	us-gaap	Proceeds From Issuance Of Secured Debt ProceedsFromIssuanceOfSecuredDebt	1181892000	USD
CY2019	us-gaap	Proceeds From Issuance Of Secured Debt ProceedsFromIssuanceOfSecuredDebt	752984000	USD
CY2018	us-gaap	Proceeds From Issuance Of Secured Debt ProceedsFromIssuanceOfSecuredDebt	564391000	USD
CY2020	us-gaap	Repayments Of Secured Debt RepaymentsOfSecuredDebt	1186828000	USD
CY2019	us-gaap	Repayments Of Secured Debt RepaymentsOfSecuredDebt	230076000	USD
CY2018	us-gaap	Repayments Of Secured Debt RepaymentsOfSecuredDebt	868842000	USD
CY2020	us-gaap	Proceeds From Issuance Of Unsecured Debt ProceedsFromIssuanceOfUnsecuredDebt	1495000000	USD
CY2019	us-gaap	Proceeds From Issuance Of Unsecured Debt ProceedsFromIssuanceOfUnsecuredDebt	1310000000	USD
CY2018	us-gaap	Proceeds From Issuance Of Unsecured Debt ProceedsFromIssuanceOfUnsecuredDebt	3120000000	USD
CY2020	us-gaap	Repayments Of Unsecured Debt RepaymentsOfUnsecuredDebt	1875000000	USD
CY2019	us-gaap	Repayments Of Unsecured Debt RepaymentsOfUnsecuredDebt	1570000000	USD
CY2018	us-gaap	Repayments Of Unsecured Debt RepaymentsOfUnsecuredDebt	2560000000	USD
CY2020	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
CY2019	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	0	USD
CY2018	us-gaap	Payments Of Debt Extinguishment Costs PaymentsOfDebtExtinguishmentCosts	13918000	USD
CY2020	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	1006000	USD
CY2019	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	334000	USD
CY2018	us-gaap	Proceeds From Stock Options Exercised ProceedsFromStockOptionsExercised	29048000	USD
CY2020	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	528483000	USD
CY2019	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	384399000	USD
CY2018	us-gaap	Payments For Repurchase Of Common Stock PaymentsForRepurchaseOfCommonStock	979541000	USD
CY2020	us-gaap	Payments For Repurchase Of Redeemable Preferred Stock PaymentsForRepurchaseOfRedeemablePreferredStock	82750000	USD
CY2019	us-gaap	Payments For Repurchase Of Redeemable Preferred Stock PaymentsForRepurchaseOfRedeemablePreferredStock	18142000	USD
CY2018	us-gaap	Payments For Repurchase Of Redeemable Preferred Stock PaymentsForRepurchaseOfRedeemablePreferredStock	1208000	USD
CY2020	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	27342000	USD
CY2019	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	27495000	USD
CY2018	us-gaap	Payments For Repurchase Of Other Equity PaymentsForRepurchaseOfOtherEquity	33972000	USD
CY2020	slg	Distributions To Noncontrolling Interests Other Partnerships DistributionsToNoncontrollingInterestsOtherPartnerships	85468000	USD
CY2019	slg	Distributions To Noncontrolling Interests Other Partnerships DistributionsToNoncontrollingInterestsOtherPartnerships	478000	USD
CY2018	slg	Distributions To Noncontrolling Interests Other Partnerships DistributionsToNoncontrollingInterestsOtherPartnerships	8364000	USD
CY2020	slg	Proceeds From Noncontrolling Interests In Other Partnerships ProceedsFromNoncontrollingInterestsInOtherPartnerships	12477000	USD
CY2019	slg	Proceeds From Noncontrolling Interests In Other Partnerships ProceedsFromNoncontrollingInterestsInOtherPartnerships	10239000	USD
CY2018	slg	Proceeds From Noncontrolling Interests In Other Partnerships ProceedsFromNoncontrollingInterestsInOtherPartnerships	5459000	USD
CY2020	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	1536000	USD
CY2019	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	25845000	USD
CY2018	us-gaap	Payments To Minority Shareholders PaymentsToMinorityShareholders	0	USD
CY2020	slg	Distribution To Noncontrolling Interest Operating Partnership DistributionToNoncontrollingInterestOperatingPartnership	12652000	USD
CY2019	slg	Distribution To Noncontrolling Interest Operating Partnership DistributionToNoncontrollingInterestOperatingPartnership	14729000	USD
CY2018	slg	Distribution To Noncontrolling Interest Operating Partnership DistributionToNoncontrollingInterestOperatingPartnership	15000000	USD
CY2020	us-gaap	Payments Of Dividends PaymentsOfDividends	293996000	USD
CY2019	us-gaap	Payments Of Dividends PaymentsOfDividends	306386000	USD
CY2018	us-gaap	Payments Of Dividends PaymentsOfDividends	313230000	USD
CY2020	slg	Proceeds From Participating Mortgage Loan ProceedsFromParticipatingMortgageLoan	0	USD
CY2019	slg	Proceeds From Participating Mortgage Loan ProceedsFromParticipatingMortgageLoan	0	USD
CY2018	slg	Proceeds From Participating Mortgage Loan ProceedsFromParticipatingMortgageLoan	16000	USD
CY2020	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	4752000	USD
CY2019	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	3495000	USD
CY2018	us-gaap	Payments Related To Tax Withholding For Share Based Compensation PaymentsRelatedToTaxWithholdingForShareBasedCompensation	3842000	USD
CY2020	us-gaap	Payments Of Financing Costs PaymentsOfFinancingCosts	70036000	USD
CY2019	us-gaap	Payments Of Financing Costs PaymentsOfFinancingCosts	21162000	USD
CY2018	us-gaap	Payments Of Financing Costs PaymentsOfFinancingCosts	15109000	USD
CY2020	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	833000	USD
CY2019	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	0	USD
CY2018	us-gaap	Finance Lease Principal Payments FinanceLeasePrincipalPayments	0	USD
CY2020	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-1479301000	USD
CY2019	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-528650000	USD
CY2018	us-gaap	Net Cash Provided By Used In Financing Activities NetCashProvidedByUsedInFinancingActivities	-1094112000	USD
CY2020	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	131365000	USD
CY2019	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	-37683000	USD
CY2018	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents Period Increase Decrease Including Exchange Rate Effect CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalentsPeriodIncreaseDecreaseIncludingExchangeRateEffect	29087000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	241430000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	279113000	USD
CY2017Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	250026000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	372795000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	241430000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	279113000	USD
CY2020	us-gaap	Interest Paid Net InterestPaidNet	201348000	USD
CY2019	us-gaap	Interest Paid Net InterestPaidNet	248684000	USD
CY2018	us-gaap	Interest Paid Net InterestPaidNet	259776000	USD
CY2020	us-gaap	Income Taxes Paid IncomeTaxesPaid	2296000	USD
CY2019	us-gaap	Income Taxes Paid IncomeTaxesPaid	1489000	USD
CY2018	us-gaap	Income Taxes Paid IncomeTaxesPaid	1418000	USD
CY2020	us-gaap	Partners Capital Account Redemptions PartnersCapitalAccountRedemptions	8744000	USD
CY2019	us-gaap	Partners Capital Account Redemptions PartnersCapitalAccountRedemptions	471000	USD
CY2018	us-gaap	Partners Capital Account Redemptions PartnersCapitalAccountRedemptions	16303000	USD
CY2020	slg	Redemption Of Units In Operating Partnership For Sale Of Joint Venture RedemptionOfUnitsInOperatingPartnershipForSaleOfJointVenture	0	USD
CY2019	slg	Redemption Of Units In Operating Partnership For Sale Of Joint Venture RedemptionOfUnitsInOperatingPartnershipForSaleOfJointVenture	0	USD
CY2018	slg	Redemption Of Units In Operating Partnership For Sale Of Joint Venture RedemptionOfUnitsInOperatingPartnershipForSaleOfJointVenture	10445000	USD
CY2020	slg	Exchange Of Preferred Equity Investment For Real Estate Or Equity In Joint Venture ExchangeOfPreferredEquityInvestmentForRealEstateOrEquityInJointVenture	119497000	USD
CY2019	slg	Exchange Of Preferred Equity Investment For Real Estate Or Equity In Joint Venture ExchangeOfPreferredEquityInvestmentForRealEstateOrEquityInJointVenture	0	USD
CY2018	slg	Exchange Of Preferred Equity Investment For Real Estate Or Equity In Joint Venture ExchangeOfPreferredEquityInvestmentForRealEstateOrEquityInJointVenture	0	USD
CY2020	us-gaap	Transfer Of Investments TransferOfInvestments	122796000	USD
CY2019	us-gaap	Transfer Of Investments TransferOfInvestments	34498000	USD
CY2018	us-gaap	Transfer Of Investments TransferOfInvestments	298956000	USD
CY2020	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	1665000	USD
CY2019	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	6056000	USD
CY2018	us-gaap	Capital Expenditures Incurred But Not Yet Paid CapitalExpendituresIncurredButNotYetPaid	0	USD
CY2020	slg	Operating Partnership Noncontrolling Interest Fair Value Adjustment OperatingPartnershipNoncontrollingInterestFairValueAdjustment	32598000	USD
CY2019	slg	Operating Partnership Noncontrolling Interest Fair Value Adjustment OperatingPartnershipNoncontrollingInterestFairValueAdjustment	34320000	USD
CY2018	slg	Operating Partnership Noncontrolling Interest Fair Value Adjustment OperatingPartnershipNoncontrollingInterestFairValueAdjustment	34236000	USD
CY2020	slg	Deconsolidation Real Estate Investments DeconsolidationRealEstateInvestments	854437000	USD
CY2019	slg	Deconsolidation Real Estate Investments DeconsolidationRealEstateInvestments	395000	USD
CY2018	slg	Deconsolidation Real Estate Investments DeconsolidationRealEstateInvestments	298404000	USD
CY2020	slg	Deconsolidation Of Subsidiary Mortgage DeconsolidationOfSubsidiaryMortgage	5593000	USD
CY2019	slg	Deconsolidation Of Subsidiary Mortgage DeconsolidationOfSubsidiaryMortgage	0	USD
CY2018	slg	Deconsolidation Of Subsidiary Mortgage DeconsolidationOfSubsidiaryMortgage	0	USD
CY2020	slg	Mortgages Assumed In Connection With Sale Of Real Estate MortgagesAssumedInConnectionWithSaleOfRealEstate	250000000	USD
CY2019	slg	Mortgages Assumed In Connection With Sale Of Real Estate MortgagesAssumedInConnectionWithSaleOfRealEstate	0	USD
CY2018	slg	Mortgages Assumed In Connection With Sale Of Real Estate MortgagesAssumedInConnectionWithSaleOfRealEstate	0	USD
CY2020	slg	Seller Financed Purchases SellerFinancedPurchases	100000000	USD
CY2019	slg	Seller Financed Purchases SellerFinancedPurchases	0	USD
CY2018	slg	Seller Financed Purchases SellerFinancedPurchases	0	USD
CY2020	slg	Debt And Preferred Equity Reserves DebtAndPreferredEquityReserves	9014000	USD
CY2018	slg	Increase Decreasein Noncontrolling Interestin Joint Ventures IncreaseDecreaseinNoncontrollingInterestinJointVentures	0	USD
CY2019	slg	Debt And Preferred Equity Reserves DebtAndPreferredEquityReserves	0	USD
CY2018	slg	Debt And Preferred Equity Reserves DebtAndPreferredEquityReserves	0	USD
CY2020	slg	Transfer To Net Assets Held For Sale TransferToNetAssetsHeldForSale	0	USD
CY2019	slg	Transfer To Net Assets Held For Sale TransferToNetAssetsHeldForSale	391664000	USD
CY2018	slg	Transfer To Net Assets Held For Sale TransferToNetAssetsHeldForSale	0	USD
CY2020	slg	Reversal Of Assets Held For Sale ReversalOfAssetsHeldForSale	391664000	USD
CY2019	slg	Reversal Of Assets Held For Sale ReversalOfAssetsHeldForSale	0	USD
CY2018	slg	Reversal Of Assets Held For Sale ReversalOfAssetsHeldForSale	0	USD
CY2020	slg	Transfer To Liabilities Related To Net Assets Held For Sale TransferToLiabilitiesRelatedToNetAssetsHeldForSale	0	USD
CY2019	slg	Transfer To Liabilities Related To Net Assets Held For Sale TransferToLiabilitiesRelatedToNetAssetsHeldForSale	0	USD
CY2018	slg	Transfer To Liabilities Related To Net Assets Held For Sale TransferToLiabilitiesRelatedToNetAssetsHeldForSale	0	USD
CY2020	slg	Removalof Fully Depreciated Real Estate Assets RemovalofFullyDepreciatedRealEstateAssets	66169000	USD
CY2019	slg	Removalof Fully Depreciated Real Estate Assets RemovalofFullyDepreciatedRealEstateAssets	19577000	USD
CY2018	slg	Removalof Fully Depreciated Real Estate Assets RemovalofFullyDepreciatedRealEstateAssets	124249000	USD
CY2020	slg	Increase Decreasein Noncontrolling Interestin Joint Ventures IncreaseDecreaseinNoncontrollingInterestinJointVentures	0	USD
CY2019	slg	Increase Decreasein Noncontrolling Interestin Joint Ventures IncreaseDecreaseinNoncontrollingInterestinJointVentures	48223000	USD
CY2020	slg	Share Repurchases Payable ShareRepurchasesPayable	3779000	USD
CY2019	slg	Share Repurchases Payable ShareRepurchasesPayable	0	USD
CY2018	slg	Share Repurchases Payable ShareRepurchasesPayable	0	USD
CY2020	slg	Recognition Of Sales Type Leases And Related Lease Liabilities RecognitionOfSalesTypeLeasesAndRelatedLeaseLiabilities	119725000	USD
CY2019	slg	Recognition Of Sales Type Leases And Related Lease Liabilities RecognitionOfSalesTypeLeasesAndRelatedLeaseLiabilities	0	USD
CY2018	slg	Recognition Of Sales Type Leases And Related Lease Liabilities RecognitionOfSalesTypeLeasesAndRelatedLeaseLiabilities	0	USD
CY2020	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	61990000	USD
CY2019	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	389120000	USD
CY2018	us-gaap	Right Of Use Asset Obtained In Exchange For Operating Lease Liability RightOfUseAssetObtainedInExchangeForOperatingLeaseLiability	0	USD
CY2020Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.3122
CY2019Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.9108
CY2018Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.8748
CY2020Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	266059000	USD
CY2019Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	166070000	USD
CY2018Q4	us-gaap	Cash And Cash Equivalents At Carrying Value CashAndCashEquivalentsAtCarryingValue	129475000	USD
CY2020Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	106736000	USD
CY2019Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	75360000	USD
CY2018Q4	us-gaap	Restricted Cash And Cash Equivalents RestrictedCashAndCashEquivalents	149638000	USD
CY2020Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	372795000	USD
CY2019Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	241430000	USD
CY2018Q4	us-gaap	Cash Cash Equivalents Restricted Cash And Restricted Cash Equivalents CashCashEquivalentsRestrictedCashAndRestrictedCashEquivalents	279113000	USD
CY2018	us-gaap	Noncontrolling Interest Decrease From Deconsolidation NoncontrollingInterestDecreaseFromDeconsolidation	315116000	USD
CY2020Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.3122
CY2019Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.9108
CY2018Q4	us-gaap	Common Stock Dividends Per Share Declared CommonStockDividendsPerShareDeclared	0.8748
CY2020Q4	us-gaap	Number Of Real Estate Properties NumberOfRealEstateProperties	69	building
CY2020Q4	us-gaap	Area Of Real Estate Property AreaOfRealEstateProperty	29500737	sqft
CY2020Q4	slg	Real Estate Weighted Average Occupancy RealEstateWeightedAverageOccupancy	0.912
CY2020	slg	Number Of Shares On Redemption Of One Unit Of Partnership Interest NumberOfSharesOnRedemptionOfOneUnitOfPartnershipInterest	1	shares
CY2020	slg	Weighted Average Amortization Period Below Market Lease Costs WeightedAverageAmortizationPeriodBelowMarketLeaseCosts	P5Y7M6D
CY2020	slg	Weighted Average Amortization Period Above Market Lease Costs WeightedAverageAmortizationPeriodAboveMarketLeaseCosts	P6Y3M18D
CY2020	slg	Weighted Average Amortization Period In Place Lease Costs WeightedAverageAmortizationPeriodInPlaceLeaseCosts	P5Y3M18D
CY2020	slg	Period From Cessation Of Major Construction Activity To Completion Of Construction Project Maximum PeriodFromCessationOfMajorConstructionActivityToCompletionOfConstructionProjectMaximum	P1Y
CY2020	slg	Commercial Real Estate Properties Depreciationand Amortization CommercialRealEstatePropertiesDepreciationandAmortization	277500000	USD
CY2019	slg	Commercial Real Estate Properties Depreciationand Amortization CommercialRealEstatePropertiesDepreciationandAmortization	233500000	USD
CY2018	slg	Commercial Real Estate Properties Depreciationand Amortization CommercialRealEstatePropertiesDepreciationandAmortization	242800000	USD
CY2020	slg	Rental Revenue Increase Decrease Acquired Lease Amortization RentalRevenueIncreaseDecreaseAcquiredLeaseAmortization	5900000	USD
CY2019	slg	Rental Revenue Increase Decrease Acquired Lease Amortization RentalRevenueIncreaseDecreaseAcquiredLeaseAmortization	4500000	USD
CY2018	slg	Rental Revenue Increase Decrease Acquired Lease Amortization RentalRevenueIncreaseDecreaseAcquiredLeaseAmortization	6800000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	215673000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Gross FiniteLivedIntangibleAssetsGross	255198000	USD
CY2020Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	190523000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Accumulated Amortization FiniteLivedIntangibleAssetsAccumulatedAmortization	228223000	USD
CY2020	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	5.54
CY2020Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	25150000	USD
CY2019Q4	us-gaap	Finite Lived Intangible Assets Net FiniteLivedIntangibleAssetsNet	26975000	USD
CY2020Q4	us-gaap	Below Market Lease Gross BelowMarketLeaseGross	241409000	USD
CY2019Q4	us-gaap	Below Market Lease Gross BelowMarketLeaseGross	282048000	USD
CY2020Q4	us-gaap	Below Market Lease Accumulated Amortization BelowMarketLeaseAccumulatedAmortization	230479000	USD
CY2019Q4	us-gaap	Below Market Lease Accumulated Amortization BelowMarketLeaseAccumulatedAmortization	249514000	USD
CY2020Q4	us-gaap	Below Market Lease Net BelowMarketLeaseNet	10930000	USD
CY2019Q4	us-gaap	Below Market Lease Net BelowMarketLeaseNet	32534000	USD
CY2020Q4	slg	Net Intangible Assets Transferredto Assets Heldfor Sale NetIntangibleAssetsTransferredtoAssetsHeldforSale	0	USD
CY2020Q4	slg	Net Intangible Liabilities Transferredto Liabilities Relatedto Assets Heldfor Sale NetIntangibleLiabilitiesTransferredtoLiabilitiesRelatedtoAssetsHeldforSale	0	USD
CY2019Q4	slg	Net Intangible Assets Transferredto Assets Heldfor Sale NetIntangibleAssetsTransferredtoAssetsHeldforSale	0	USD
CY2019Q4	slg	Net Intangible Liabilities Transferredto Liabilities Relatedto Assets Heldfor Sale NetIntangibleLiabilitiesTransferredtoLiabilitiesRelatedtoAssetsHeldforSale	0	USD
CY2020	slg	Deferred Lease Costs Capitalized In Period DeferredLeaseCostsCapitalizedInPeriod	5400000	USD
CY2019	slg	Deferred Lease Costs Capitalized In Period DeferredLeaseCostsCapitalizedInPeriod	6300000	USD
CY2018	slg	Deferred Lease Costs Capitalized In Period DeferredLeaseCostsCapitalizedInPeriod	15700000	USD
CY2020	slg	Operating Leases Estimated Average Lease Term OperatingLeasesEstimatedAverageLeaseTerm	P8Y
CY2020	slg	Financing Receivable Number Of Days Past Due For Suspending Income Recognition FinancingReceivableNumberOfDaysPastDueForSuspendingIncomeRecognition	P90D
CY2020	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1200000	USD
CY2019	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	1500000	USD
CY2018	us-gaap	Income Tax Expense Benefit IncomeTaxExpenseBenefit	2800000	USD
CY2019	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	3.40
CY2018	us-gaap	Common Stock Dividends Per Share Cash Paid CommonStockDividendsPerShareCashPaid	3.25
CY2020	us-gaap	Use Of Estimates UseOfEstimates	<div style="margin-bottom:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Use of Estimates</span></div><div style="margin-bottom:6pt;text-align:justify;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">The preparation of financial statements in conformity with accounting principles generally accepted in the United States requires management to make estimates and assumptions that affect the amounts reported in the financial statements and accompanying notes. Actual results could differ from those estimates.</span></div>
CY2020	us-gaap	Concentration Risk Credit Risk ConcentrationRiskCreditRisk	<div style="margin-bottom:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Concentrations of Credit Risk</span></div><div style="margin-bottom:6pt;text-align:justify;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Financial instruments that potentially subject us to concentrations of credit risk consist primarily of cash investments, debt and preferred equity investments and accounts receivable. We place our cash investments with high quality financial institutions. The collateral securing our debt and preferred equity investments is located in New York City. See Note 5, "Debt and Preferred Equity Investments." </span></div>We perform initial and ongoing evaluations of the credit quality of our tenants and require most tenants to provide security deposits or letters of credit. Though these security deposits and letters of credit are insufficient to meet the total value of a tenant's lease obligation, they are a measure of good faith and a potential source of funds to offset the economic costs associated with lost revenue from the tenant and the costs associated with re-tenanting a space. The properties in our real estate portfolio are located in the New York metropolitan area. The tenants located in our buildings operate in various industries.
CY2020	us-gaap	Prior Period Reclassification Adjustment Description PriorPeriodReclassificationAdjustmentDescription	<div style="margin-bottom:6pt;text-align:justify"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:700;line-height:120%">Reclassification</span></div><div style="margin-bottom:6pt;text-align:justify;text-indent:24.75pt"><span style="color:#000000;font-family:'Times New Roman',sans-serif;font-size:10pt;font-weight:400;line-height:120%">Certain prior year balances have been reclassified to conform to our current year presentation.</span></div>
CY2019Q4	us-gaap	Mortgage Loans On Real Estate MortgageLoansOnRealEstate	1580306000	USD
CY2020	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	37033000	USD
CY2018Q4	us-gaap	Mortgage Loans On Real Estate MortgageLoansOnRealEstate	2099393000	USD
CY2020	us-gaap	Mortgage Loans On Real Estate Amortization Of Premium MortgageLoansOnRealEstateAmortizationOfPremium	1048643000	USD
CY2019	us-gaap	Mortgage Loans On Real Estate Amortization Of Premium MortgageLoansOnRealEstateAmortizationOfPremium	1190689000	USD
CY2020	slg	Sec Schedule1229 Real Estate Companies Investment In Mortgage Loans On Real Estate Loan Loss Reserve Period Increase Decrease SECSchedule1229RealEstateCompaniesInvestmentInMortgageLoansOnRealEstateLoanLossReservePeriodIncreaseDecrease	-11463000	USD
CY2019	slg	Sec Schedule1229 Real Estate Companies Investment In Mortgage Loans On Real Estate Loan Loss Reserve Period Increase Decrease SECSchedule1229RealEstateCompaniesInvestmentInMortgageLoansOnRealEstateLoanLossReservePeriodIncreaseDecrease	4000000	USD
CY2020Q4	us-gaap	Mortgage Loans On Real Estate MortgageLoansOnRealEstate	1076542000	USD
CY2019Q4	us-gaap	Mortgage Loans On Real Estate MortgageLoansOnRealEstate	1580306000	USD
CY2020Q4	us-gaap	Mortgage Loans On Real Estate Commercial And Consumer Net MortgageLoansOnRealEstateCommercialAndConsumerNet	1076542000	USD
CY2020Q4	slg	Mortgage Loanson Real Estate Senior Financing MortgageLoansonRealEstateSeniorFinancing	6549037000	USD
CY2019Q4	us-gaap	Allowance For Loan And Lease Losses Real Estate AllowanceForLoanAndLeaseLossesRealEstate	1750000	USD
CY2018Q4	us-gaap	Allowance For Loan And Lease Losses Real Estate AllowanceForLoanAndLeaseLossesRealEstate	5750000	USD
CY2017Q4	us-gaap	Allowance For Loan And Lease Losses Real Estate AllowanceForLoanAndLeaseLossesRealEstate	0	USD
CY2020	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	20693000	USD
CY2019	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	0	USD
CY2018	us-gaap	Provision For Loan Losses Expensed ProvisionForLoanLossesExpensed	6839000	USD
CY2019	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	4000000	USD
CY2018	us-gaap	Financing Receivable Allowance For Credit Losses Write Offs FinancingReceivableAllowanceForCreditLossesWriteOffs	1089000	USD
CY2020Q4	us-gaap	Allowance For Loan And Lease Losses Real Estate AllowanceForLoanAndLeaseLossesRealEstate	13213000	USD
CY2019Q4	us-gaap	Allowance For Loan And Lease Losses Real Estate AllowanceForLoanAndLeaseLossesRealEstate	1750000	USD
CY2018Q4	us-gaap	Allowance For Loan And Lease Losses Real Estate AllowanceForLoanAndLeaseLossesRealEstate	5750000	USD
CY2020Q4	slg	Financing Receivable Nonaccrual No Allowance Number FinancingReceivableNonaccrualNoAllowanceNumber	1	loan
CY2020Q4	us-gaap	Financing Receivable Nonaccrual No Allowance FinancingReceivableNonaccrualNoAllowance	225200000	USD
CY2020Q4	slg	Number Of Investments Nonperforming NumberOfInvestmentsNonperforming	1	investment
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	1076542000	USD
CY2019Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	1580306000	USD
CY2020Q4	us-gaap	Financing Receivable Originated In Current Fiscal Year FinancingReceivableOriginatedInCurrentFiscalYear	346320000	USD
CY2020Q4	us-gaap	Financing Receivable Originated In Fiscal Year Before Latest Fiscal Year FinancingReceivableOriginatedInFiscalYearBeforeLatestFiscalYear	294533000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Two Years Before Latest Fiscal Year FinancingReceivableOriginatedTwoYearsBeforeLatestFiscalYear	266185000	USD
CY2020Q4	us-gaap	Financing Receivable Originated Three Years Before Latest Fiscal Year FinancingReceivableOriginatedThreeYearsBeforeLatestFiscalYear	169504000	USD
CY2020Q4	us-gaap	Notes Receivable Gross NotesReceivableGross	1076542000	USD
CY2020	slg	Financing Receivable Portfolio Segments Number FinancingReceivablePortfolioSegmentsNumber	1	segment
CY2019	slg	Financing Receivable Portfolio Segments Number FinancingReceivablePortfolioSegmentsNumber	1	segment
CY2020Q4	slg	Financing Receivable Recorded In Other Assets FinancingReceivableRecordedInOtherAssets	66200000	USD
CY2019Q4	slg	Financing Receivable Recorded In Other Assets FinancingReceivableRecordedInOtherAssets	131100000	USD
CY2020Q4	us-gaap	Financing Receivable Recorded Investment Nonaccrual Status FinancingReceivableRecordedInvestmentNonaccrualStatus	2500000	USD
CY2020	srt	Mortgage Loans On Real Estate Interest Rate MortgageLoansOnRealEstateInterestRate	0.0580
CY2020Q4	slg	Variable Interest Entity Not Primary Beneficiary Investment VariableInterestEntityNotPrimaryBeneficiaryInvestment	134000000.0	USD
CY2019Q4	slg	Variable Interest Entity Not Primary Beneficiary Investment VariableInterestEntityNotPrimaryBeneficiaryInvestment	145900000	USD
CY2020Q4	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	0.0	USD
CY2019Q4	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	4000000.0	USD
CY2018Q4	us-gaap	Employee Related Liabilities Current And Noncurrent EmployeeRelatedLiabilitiesCurrentAndNoncurrent	11700000	USD
CY2019Q4	us-gaap	Equity Method Investments EquityMethodInvestments	2912842000	USD
CY2020Q4	us-gaap	Equity Method Investment Difference Between Carrying Amount And Underlying Equity EquityMethodInvestmentDifferenceBetweenCarryingAmountAndUnderlyingEquity	170600000	USD
CY2020Q4	us-gaap	Deferred Costs Leasing Gross DeferredCostsLeasingGross	447002000	USD
CY2019Q4	us-gaap	Deferred Costs Leasing Gross DeferredCostsLeasingGross	466136000	USD
CY2020Q4	us-gaap	Deferred Costs Leasing Accumulated Amortization DeferredCostsLeasingAccumulatedAmortization	269834000	USD
CY2019Q4	us-gaap	Deferred Costs Leasing Accumulated Amortization DeferredCostsLeasingAccumulatedAmortization	260853000	USD
CY2020Q4	us-gaap	Deferred Costs Leasing Net DeferredCostsLeasingNet	177168000	USD
CY2019Q4	us-gaap	Deferred Costs Leasing Net DeferredCostsLeasingNet	205283000	USD
CY2020Q4	slg	Secured Debt Bearing Fixed Interest Amount SecuredDebtBearingFixedInterestAmount	1083683000	USD
CY2019Q4	slg	Secured Debt Bearing Fixed Interest Amount SecuredDebtBearingFixedInterestAmount	1383449000	USD
CY2020Q4	slg	Secured Debt Bearing Variable Interest Amount SecuredDebtBearingVariableInterestAmount	917677000	USD
CY2019Q4	slg	Secured Debt Bearing Variable Interest Amount SecuredDebtBearingVariableInterestAmount	828434000	USD
CY2020Q4	slg	Secured Debt Gross SecuredDebtGross	2001360000	USD
CY2019Q4	slg	Secured Debt Gross SecuredDebtGross	2211883000	USD
CY2020Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	21388000	USD
CY2019Q4	us-gaap	Deferred Finance Costs Net DeferredFinanceCostsNet	28630000	USD
CY2020Q4	us-gaap	Long Term Debt LongTermDebt	1979972000	USD
CY2019Q4	us-gaap	Long Term Debt LongTermDebt	2183253000	USD
CY2020Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	2500000000	USD
CY2019Q4	us-gaap	Collateral Already Posted Aggregate Fair Value CollateralAlreadyPostedAggregateFairValue	3300000000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Next Twelve Months LongTermDebtMaturitiesRepaymentsOfPrincipalInNextTwelveMonths	660727000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Two LongTermDebtMaturitiesRepaymentsOfPrincipalInYearTwo	1064202000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Three LongTermDebtMaturitiesRepaymentsOfPrincipalInYearThree	1976599000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Four LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFour	478034000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal In Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalInYearFive	100829000	USD
CY2020Q4	us-gaap	Long Term Debt Maturities Repayments Of Principal After Year Five LongTermDebtMaturitiesRepaymentsOfPrincipalAfterYearFive	680969000	USD
CY2020Q4	slg	Long Term Debt Maturities Repayments Of Principal LongTermDebtMaturitiesRepaymentsOfPrincipal	4961360000	USD
CY2020	us-gaap	Interest Expense InterestExpense	185934000	USD
CY2019	us-gaap	Interest Expense InterestExpense	246848000	USD
CY2018	us-gaap	Interest Expense InterestExpense	236719000	USD
CY2020	slg	Finance Lease Interest Expense Before Capitalized Interest FinanceLeaseInterestExpenseBeforeCapitalizedInterest	8091000	USD
CY2019	slg	Finance Lease Interest Expense Before Capitalized Interest FinanceLeaseInterestExpenseBeforeCapitalizedInterest	3243000	USD
CY2018	slg	Finance Lease Interest Expense Before Capitalized Interest FinanceLeaseInterestExpenseBeforeCapitalizedInterest	8069000	USD
CY2020	us-gaap	Interest Costs Incurred Capitalized InterestCostsIncurredCapitalized	75167000	USD
CY2019	us-gaap	Interest Costs Incurred Capitalized InterestCostsIncurredCapitalized	55446000	USD
CY2018	us-gaap	Interest Costs Incurred Capitalized InterestCostsIncurredCapitalized	34162000	USD
CY2020	us-gaap	Interest Income Operating InterestIncomeOperating	2179000	USD
CY2019	us-gaap	Interest Income Operating InterestIncomeOperating	4124000	USD
CY2018	us-gaap	Interest Income Operating InterestIncomeOperating	1957000	USD
CY2020	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	-116679000	USD
CY2019	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	-190521000	USD
CY2018	us-gaap	Interest Income Expense Net InterestIncomeExpenseNet	-208669000	USD
CY2020Q4	us-gaap	Due From Joint Ventures DueFromJointVentures	27006000	USD
CY2019Q4	us-gaap	Due From Joint Ventures DueFromJointVentures	9352000	USD
CY2020Q4	us-gaap	Due From Other Related Parties DueFromOtherRelatedParties	7651000	USD
CY2019Q4	us-gaap	Due From Other Related Parties DueFromOtherRelatedParties	11769000	USD
CY2020Q4	us-gaap	Due From Related Parties DueFromRelatedParties	34657000	USD
CY2019Q4	us-gaap	Due From Related Parties DueFromRelatedParties	21121000	USD
CY2020Q4	slg	Total Shares Authorized TotalSharesAuthorized	260000000	shares
CY2020Q4	slg	Total Par Or Stated Value Per Share TotalParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Common Stock Shares Authorized CommonStockSharesAuthorized	160000000	shares
CY2020Q4	us-gaap	Common Stock Par Or Stated Value Per Share CommonStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Excess Stock Shares Authorized ExcessStockSharesAuthorized	75000000	shares
CY2020Q4	slg	Excess Stock Par Or Stated Value Per Share ExcessStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Preferred Stock Shares Authorized PreferredStockSharesAuthorized	25000000	shares
CY2020Q4	us-gaap	Preferred Stock Par Or Stated Value Per Share PreferredStockParOrStatedValuePerShare	0.01
CY2020Q4	us-gaap	Excess Stock Shares Issued ExcessStockSharesIssued	0	shares
CY2017	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	8105881	shares
CY2017	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	104.61
CY2018	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	9468617	shares
CY2018	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	99.03
CY2019	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	4465857	shares
CY2019	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	86.06
CY2020	us-gaap	Stock Repurchased During Period Shares StockRepurchasedDuringPeriodShares	8538995	shares
CY2020	us-gaap	Treasury Stock Acquired Average Cost Per Share TreasuryStockAcquiredAverageCostPerShare	62.39
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	356105000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	255484000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Basic NetIncomeLossAvailableToCommonStockholdersBasic	232312000	USD
CY2020	slg	Net Income Loss Available To Common Stockholders After Distributed And Undistributed Earnings Allocation Basic NetIncomeLossAvailableToCommonStockholdersAfterDistributedAndUndistributedEarningsAllocationBasic	354335000	USD
CY2019	slg	Net Income Loss Available To Common Stockholders After Distributed And Undistributed Earnings Allocation Basic NetIncomeLossAvailableToCommonStockholdersAfterDistributedAndUndistributedEarningsAllocationBasic	253782000	USD
CY2018	slg	Net Income Loss Available To Common Stockholders After Distributed And Undistributed Earnings Allocation Basic NetIncomeLossAvailableToCommonStockholdersAfterDistributedAndUndistributedEarningsAllocationBasic	231270000	USD
CY2020	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Diluted UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted	-1770000	USD
CY2019	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Diluted UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted	-1702000	USD
CY2018	us-gaap	Undistributed Earnings Loss Allocated To Participating Securities Diluted UndistributedEarningsLossAllocatedToParticipatingSecuritiesDiluted	-1042000	USD
CY2020	us-gaap	Dilutive Securities Effect On Basic Earnings Per Share Other DilutiveSecuritiesEffectOnBasicEarningsPerShareOther	20016000	USD
CY2019	us-gaap	Dilutive Securities Effect On Basic Earnings Per Share Other DilutiveSecuritiesEffectOnBasicEarningsPerShareOther	13301000	USD
CY2018	us-gaap	Dilutive Securities Effect On Basic Earnings Per Share Other DilutiveSecuritiesEffectOnBasicEarningsPerShareOther	12216000	USD
CY2020	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	376121000	USD
CY2019	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	268785000	USD
CY2018	us-gaap	Net Income Loss Available To Common Stockholders Diluted NetIncomeLossAvailableToCommonStockholdersDiluted	244528000	USD
CY2020	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	72552000	shares
CY2019	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	79415000	shares
CY2018	us-gaap	Weighted Average Number Of Shares Outstanding Basic WeightedAverageNumberOfSharesOutstandingBasic	84090000	shares
CY2020	slg	Incremental Common Shares Attributable To Redemption Of Units To Common Shares IncrementalCommonSharesAttributableToRedemptionOfUnitsToCommonShares	4096000	shares
CY2019	slg	Incremental Common Shares Attributable To Redemption Of Units To Common Shares IncrementalCommonSharesAttributableToRedemptionOfUnitsToCommonShares	4275000	shares
CY2018	slg	Incremental Common Shares Attributable To Redemption Of Units To Common Shares IncrementalCommonSharesAttributableToRedemptionOfUnitsToCommonShares	4562000	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	440000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	544000	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Share Based Payment Arrangements IncrementalCommonSharesAttributableToShareBasedPaymentArrangements	419000	shares
CY2020	us-gaap	Incremental Common Shares Attributable To Contingently Issuable Shares IncrementalCommonSharesAttributableToContingentlyIssuableShares	155000	shares
CY2019	us-gaap	Incremental Common Shares Attributable To Contingently Issuable Shares IncrementalCommonSharesAttributableToContingentlyIssuableShares	0	shares
CY2018	us-gaap	Incremental Common Shares Attributable To Contingently Issuable Shares IncrementalCommonSharesAttributableToContingentlyIssuableShares	0	shares
CY2020	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	77243000	shares
CY2019	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	84234000	shares
CY2018	us-gaap	Weighted Average Number Of Diluted Shares Outstanding WeightedAverageNumberOfDilutedSharesOutstanding	89071000	shares
CY2020	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1728136	shares
CY2019	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1217153	shares
CY2018	us-gaap	Antidilutive Securities Excluded From Computation Of Earnings Per Share Amount AntidilutiveSecuritiesExcludedFromComputationOfEarningsPerShareAmount	1106363	shares
CY2020	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	2200000	USD
CY2019	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	2100000	USD
CY2018	us-gaap	Employee Service Share Based Compensation Allocation Of Recognized Period Costs Capitalized Amount EmployeeServiceShareBasedCompensationAllocationOfRecognizedPeriodCostsCapitalizedAmount	6300000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-2304000	USD
CY2018	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	1192000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-43495000	USD
CY2019	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	98000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Before Reclassifications Net Of Tax OtherComprehensiveIncomeLossBeforeReclassificationsNetOfTax	-57361000	USD
CY2020	us-gaap	Reclassification From Accumulated Other Comprehensive Income Current Period Net Of Tax ReclassificationFromAccumulatedOtherComprehensiveIncomeCurrentPeriodNetOfTax	-18599000	USD
CY2020Q4	slg	Other Comprehensive Income Loss Deferred Net Lossfrom Terminated Hedges OtherComprehensiveIncomeLossDeferredNetLossfromTerminatedHedges	-500000	USD
CY2019Q4	slg	Other Comprehensive Income Loss Deferred Net Lossfrom Terminated Hedges OtherComprehensiveIncomeLossDeferredNetLossfromTerminatedHedges	-700000	USD
CY2020Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	28570000	USD
CY2020Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	28000	USD
CY2019Q4	us-gaap	Available For Sale Securities Debt Securities AvailableForSaleSecuritiesDebtSecurities	29887000	USD
CY2019Q4	us-gaap	Derivative Fair Value Of Derivative Asset DerivativeFairValueOfDerivativeAsset	4419000	USD
CY2018	us-gaap	Asset Impairment Charges AssetImpairmentCharges	221900000	USD
CY2020	slg	Accumulated Other Comprehensive Income Loss Gain Lossfrom Changesin Fair Value AccumulatedOtherComprehensiveIncomeLossGainLossfromChangesinFairValue	-100000	USD
CY2019	slg	Accumulated Other Comprehensive Income Loss Gain Lossfrom Changesin Fair Value AccumulatedOtherComprehensiveIncomeLossGainLossfromChangesinFairValue	-100000	USD
CY2018	slg	Accumulated Other Comprehensive Income Loss Gain Lossfrom Changesin Fair Value AccumulatedOtherComprehensiveIncomeLossGainLossfromChangesinFairValue	-200000	USD
CY2020Q4	us-gaap	Derivative Net Liability Position Aggregate Fair Value DerivativeNetLiabilityPositionAggregateFairValue	62500000	USD
CY2020Q4	us-gaap	Assets Needed For Immediate Settlement Aggregate Fair Value AssetsNeededForImmediateSettlementAggregateFairValue	63600000	USD
CY2019	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	983557000	USD
CY2020	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-59221000	USD
CY2019	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-44229000	USD
CY2018	us-gaap	Other Comprehensive Income Loss Cash Flow Hedge Gain Loss Before Reclassification And Tax OtherComprehensiveIncomeLossCashFlowHedgeGainLossBeforeReclassificationAndTax	-4072000	USD
CY2020	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	19480000	USD
CY2019	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	5000	USD
CY2018	us-gaap	Interest Rate Cash Flow Hedge Gain Loss Reclassified To Earnings Net InterestRateCashFlowHedgeGainLossReclassifiedToEarningsNet	-2265000	USD
CY2020Q4	us-gaap	Lessor Operating Lease Payments To Be Received Next Twelve Months LessorOperatingLeasePaymentsToBeReceivedNextTwelveMonths	631775000	USD
CY2020Q4	us-gaap	Lessor Operating Lease Payments To Be Received Two Years LessorOperatingLeasePaymentsToBeReceivedTwoYears	598226000	USD
CY2020Q4	us-gaap	Lessor Operating Lease Payments To Be Received Three Years LessorOperatingLeasePaymentsToBeReceivedThreeYears	546803000	USD
CY2020Q4	us-gaap	Sales Type Lease Net Investment In Lease SalesTypeLeaseNetInvestmentInLease	149399000	USD
CY2020Q4	us-gaap	Lessor Operating Lease Payments To Be Received Four Years LessorOperatingLeasePaymentsToBeReceivedFourYears	511087000	USD
CY2020Q4	us-gaap	Lessor Operating Lease Payments To Be Received Five Years LessorOperatingLeasePaymentsToBeReceivedFiveYears	465398000	USD
CY2020Q4	us-gaap	Lessor Operating Lease Payments To Be Received Thereafter LessorOperatingLeasePaymentsToBeReceivedThereafter	2658793000	USD
CY2020Q4	us-gaap	Lessor Operating Lease Payments To Be Received LessorOperatingLeasePaymentsToBeReceived	5412082000	USD
CY2020	us-gaap	Operating Lease Lease Income Lease Payments OperatingLeaseLeaseIncomeLeasePayments	702482000	USD
CY2019	us-gaap	Operating Lease Lease Income Lease Payments OperatingLeaseLeaseIncomeLeasePayments	858587000	USD
CY2020	us-gaap	Operating Lease Variable Lease Income OperatingLeaseVariableLeaseIncome	96040000	USD
CY2019	us-gaap	Operating Lease Variable Lease Income OperatingLeaseVariableLeaseIncome	120496000	USD
CY2020	slg	Operating Lease Lease Income Fixed And Variable Lease Payments OperatingLeaseLeaseIncomeFixedAndVariableLeasePayments	798522000	USD
CY2019	slg	Operating Lease Lease Income Fixed And Variable Lease Payments OperatingLeaseLeaseIncomeFixedAndVariableLeasePayments	979083000	USD
CY2020	us-gaap	Amortization Of Above And Below Market Leases AmortizationOfAboveAndBelowMarketLeases	5901000	USD
CY2019	us-gaap	Amortization Of Above And Below Market Leases AmortizationOfAboveAndBelowMarketLeases	4474000	USD
CY2020	us-gaap	Operating Lease Lease Income OperatingLeaseLeaseIncome	804423000	USD
CY2020	slg	Operating Leases Minimum Lease Term OperatingLeasesMinimumLeaseTerm	P1Y
CY2020Q4	us-gaap	Sales Type And Direct Financing Leases Lease Receivable Payments To Be Received Next Twelve Months SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedNextTwelveMonths	46326000	USD
CY2020Q4	us-gaap	Sales Type And Direct Financing Leases Lease Receivable Payments To Be Received Two Years SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedTwoYears	3375000	USD
CY2020Q4	us-gaap	Sales Type And Direct Financing Leases Lease Receivable Payments To Be Received Three Years SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedThreeYears	3424000	USD
CY2020Q4	us-gaap	Sales Type And Direct Financing Leases Lease Receivable Payments To Be Received Four Years SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedFourYears	3474000	USD
CY2020Q4	us-gaap	Sales Type And Direct Financing Leases Lease Receivable Payments To Be Received Five Years SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedFiveYears	3525000	USD
CY2020Q4	us-gaap	Sales Type And Direct Financing Leases Lease Receivable Payments To Be Received Thereafter SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceivedThereafter	223199000	USD
CY2020Q4	us-gaap	Sales Type And Direct Financing Leases Lease Receivable Payments To Be Received SalesTypeAndDirectFinancingLeasesLeaseReceivablePaymentsToBeReceived	283323000	USD
CY2020Q4	us-gaap	Sales Type And Direct Financing Leases Lease Receivable Undiscounted Excess Amount SalesTypeAndDirectFinancingLeasesLeaseReceivableUndiscountedExcessAmount	133924000	USD
CY2020	us-gaap	Sales Type Lease Selling Profit Loss SalesTypeLeaseSellingProfitLoss	-6237000	USD
CY2019	us-gaap	Sales Type Lease Selling Profit Loss SalesTypeLeaseSellingProfitLoss	0	USD
CY2020	us-gaap	Sales Type Lease Interest Income SalesTypeLeaseInterestIncome	1817000	USD
CY2019	us-gaap	Sales Type Lease Interest Income SalesTypeLeaseInterestIncome	0	USD
CY2020	us-gaap	Multiemployer Plan Pension Significant Plan Contribution MultiemployerPlanPensionSignificantPlanContribution	11097000	USD
CY2019	us-gaap	Multiemployer Plan Pension Significant Plan Contribution MultiemployerPlanPensionSignificantPlanContribution	14160000	USD
CY2018	us-gaap	Multiemployer Plan Pension Significant Plan Contribution MultiemployerPlanPensionSignificantPlanContribution	13433000	USD
CY2020	us-gaap	Defined Contribution Plan Maximum Annual Contributions Per Employee Percent DefinedContributionPlanMaximumAnnualContributionsPerEmployeePercent	0.15
CY2020	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent Of Match DefinedContributionPlanEmployerMatchingContributionPercentOfMatch	1
CY2019	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent Of Match DefinedContributionPlanEmployerMatchingContributionPercentOfMatch	1
CY2020	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent DefinedContributionPlanEmployerMatchingContributionPercent	0.04
CY2019	us-gaap	Defined Contribution Plan Employer Matching Contribution Percent DefinedContributionPlanEmployerMatchingContributionPercent	0.04
CY2020	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	1700000	USD
CY2020Q4	us-gaap	Finance Lease Liability FinanceLeaseLiability	152521000	USD
CY2020Q4	us-gaap	Operating Lease Liability OperatingLeaseLiability	339458000	USD
CY2020	slg	Operating Lease Cost Before Capitalized Operating Lease Costs OperatingLeaseCostBeforeCapitalizedOperatingLeaseCosts	32169000	USD
CY2019	slg	Operating Lease Cost Before Capitalized Operating Lease Costs OperatingLeaseCostBeforeCapitalizedOperatingLeaseCosts	33235000	USD
CY2019	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	1600000	USD
CY2018	us-gaap	Defined Contribution Plan Cost Recognized DefinedContributionPlanCostRecognized	1100000	USD
CY2020Q4	slg	Employment Agreements Minimum Cash Based Compensation In Next Fiscal Year EmploymentAgreementsMinimumCashBasedCompensationInNextFiscalYear	3400000	USD
CY2020	slg	Operating Leases Minimum Lease Term OperatingLeasesMinimumLeaseTerm	P1Y
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Next Twelve Months FinanceLeaseLiabilityPaymentsDueNextTwelveMonths	32527000	USD
CY2020	slg	Operating Lease Cost Capitalized OperatingLeaseCostCapitalized	3127000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Next Twelve Months LesseeOperatingLeaseLiabilityPaymentsDueNextTwelveMonths	28534000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Two FinanceLeaseLiabilityPaymentsDueYearTwo	3523000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Two LesseeOperatingLeaseLiabilityPaymentsDueYearTwo	26228000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Three FinanceLeaseLiabilityPaymentsDueYearThree	3570000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Three LesseeOperatingLeaseLiabilityPaymentsDueYearThree	23921000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Four FinanceLeaseLiabilityPaymentsDueYearFour	3641000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Four LesseeOperatingLeaseLiabilityPaymentsDueYearFour	23939000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due Year Five FinanceLeaseLiabilityPaymentsDueYearFive	3810000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due Year Five LesseeOperatingLeaseLiabilityPaymentsDueYearFive	24026000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due After Year Five FinanceLeaseLiabilityPaymentsDueAfterYearFive	260550000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due After Year Five LesseeOperatingLeaseLiabilityPaymentsDueAfterYearFive	504360000	USD
CY2020Q4	us-gaap	Finance Lease Liability Payments Due FinanceLeaseLiabilityPaymentsDue	307621000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Payments Due LesseeOperatingLeaseLiabilityPaymentsDue	631008000	USD
CY2020Q4	us-gaap	Finance Lease Liability Undiscounted Excess Amount FinanceLeaseLiabilityUndiscountedExcessAmount	155100000	USD
CY2020Q4	us-gaap	Lessee Operating Lease Liability Undiscounted Excess Amount LesseeOperatingLeaseLiabilityUndiscountedExcessAmount	291550000	USD
CY2019	slg	Operating Lease Cost Capitalized OperatingLeaseCostCapitalized	47000	USD
CY2020	us-gaap	Operating Lease Cost OperatingLeaseCost	29043000	USD
CY2019	us-gaap	Operating Lease Cost OperatingLeaseCost	33188000	USD
CY2020	slg	Finance Lease Interest Expense Before Capitalized Interest FinanceLeaseInterestExpenseBeforeCapitalizedInterest	8091000	USD
CY2019	slg	Finance Lease Interest Expense Before Capitalized Interest FinanceLeaseInterestExpenseBeforeCapitalizedInterest	3243000	USD
CY2020	slg	Finance Lease Interest Expense Capitalized FinanceLeaseInterestExpenseCapitalized	2378000	USD
CY2019	slg	Finance Lease Interest Expense Capitalized FinanceLeaseInterestExpenseCapitalized	0	USD
CY2020	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	5713000	USD
CY2019	us-gaap	Finance Lease Interest Expense FinanceLeaseInterestExpense	3243000	USD
CY2020	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	1200000	USD
CY2019	us-gaap	Finance Lease Right Of Use Asset Amortization FinanceLeaseRightOfUseAssetAmortization	1219000	USD
CY2020	slg	Finance Lease Cost FinanceLeaseCost	6913000	USD
CY2019	slg	Finance Lease Cost FinanceLeaseCost	4462000	USD
CY2020Q4	us-gaap	Operating Lease Weighted Average Discount Rate Percent OperatingLeaseWeightedAverageDiscountRatePercent	0.0471
CY2020Q4	us-gaap	Operating Lease Weighted Average Remaining Lease Term1 OperatingLeaseWeightedAverageRemainingLeaseTerm1	P27Y
CY2020	us-gaap	Number Of Reportable Segments NumberOfReportableSegments	2	segment
CY2019	slg	Income Loss From Continuing Operations Before Realized Gain Loss On Disposal Of Equity Method Investment IncomeLossFromContinuingOperationsBeforeRealizedGainLossOnDisposalOfEquityMethodInvestment	291487000	USD
CY2020	us-gaap	Revenues Revenues	1052744000	USD
CY2019	us-gaap	Revenues Revenues	1238995000	USD
CY2018	us-gaap	Revenues Revenues	1227392000	USD
CY2020	slg	Income Loss From Continuing Operations Before Realized Gain Loss On Disposal Of Equity Method Investment IncomeLossFromContinuingOperationsBeforeRealizedGainLossOnDisposalOfEquityMethodInvestment	414758000	USD
CY2018	slg	Income Loss From Continuing Operations Before Realized Gain Loss On Disposal Of Equity Method Investment IncomeLossFromContinuingOperationsBeforeRealizedGainLossOnDisposalOfEquityMethodInvestment	270856000	USD
CY2020Q4	us-gaap	Assets Assets	11707567000	USD
CY2019Q4	us-gaap	Assets Assets	12766320000	USD
CY2020	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	91800000	USD
CY2019	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	100900000	USD
CY2018	us-gaap	Selling General And Administrative Expense SellingGeneralAndAdministrativeExpense	92600000	USD
CY2020Q4	srt	Real Estate And Accumulated Depreciation Amount Of Encumbrances RealEstateAndAccumulatedDepreciationAmountOfEncumbrances	1941360000	USD
CY2020Q4	us-gaap	Real Estate And Accumulated Depreciation Initial Cost Of Land RealEstateAndAccumulatedDepreciationInitialCostOfLand	1336041000	USD
CY2020Q4	us-gaap	Real Estate And Accumulated Depreciation Initial Cost Of Buildings And Improvements RealEstateAndAccumulatedDepreciationInitialCostOfBuildingsAndImprovements	5305161000	USD
CY2020Q4	slg	Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Of Land RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionOfLand	-20207000	USD
CY2020Q4	slg	Real Estate And Accumulated Depreciation Costs Capitalized Subsequent To Acquisition Of Building And Improvements RealEstateAndAccumulatedDepreciationCostsCapitalizedSubsequentToAcquisitionOfBuildingAndImprovements	734086000	USD
CY2020Q4	us-gaap	Real Estate And Accumulated Depreciation Carrying Amount Of Land RealEstateAndAccumulatedDepreciationCarryingAmountOfLand	1315832000	USD
CY2020Q4	us-gaap	Real Estate And Accumulated Depreciation Carrying Amount Of Buildings And Improvements RealEstateAndAccumulatedDepreciationCarryingAmountOfBuildingsAndImprovements	6039247000	USD
CY2020Q4	us-gaap	Real Estate Gross At Carrying Value RealEstateGrossAtCarryingValue	7355079000	USD
CY2020Q4	us-gaap	Real Estate Accumulated Depreciation RealEstateAccumulatedDepreciation	1956077000	USD
CY2019Q4	us-gaap	Real Estate Gross At Carrying Value RealEstateGrossAtCarryingValue	8784567000	USD
CY2018Q4	us-gaap	Real Estate Gross At Carrying Value RealEstateGrossAtCarryingValue	8513935000	USD
CY2017Q4	us-gaap	Real Estate Gross At Carrying Value RealEstateGrossAtCarryingValue	10206122000	USD
CY2020	us-gaap	Real Estate Other Acquisitions RealEstateOtherAcquisitions	178635000	USD
CY2019	us-gaap	Real Estate Other Acquisitions RealEstateOtherAcquisitions	0	USD
CY2018	us-gaap	Real Estate Other Acquisitions RealEstateOtherAcquisitions	52939000	USD
CY2020	us-gaap	Real Estate Improvements RealEstateImprovements	481327000	USD
CY2019	us-gaap	Real Estate Improvements RealEstateImprovements	251674000	USD
CY2018	us-gaap	Sec Schedule Iii Real Estate Accumulated Depreciation Depreciation Expense SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense	245033000	USD
CY2018	us-gaap	Real Estate Improvements RealEstateImprovements	267726000	USD
CY2020	slg	Real Estate Cost Of Real Estate Sold Retired Or Deconsolidated RealEstateCostOfRealEstateSoldRetiredOrDeconsolidated	2089450000	USD
CY2019	slg	Real Estate Cost Of Real Estate Sold Retired Or Deconsolidated RealEstateCostOfRealEstateSoldRetiredOrDeconsolidated	-18958000	USD
CY2018	slg	Real Estate Cost Of Real Estate Sold Retired Or Deconsolidated RealEstateCostOfRealEstateSoldRetiredOrDeconsolidated	2012852000	USD
CY2020Q4	us-gaap	Real Estate Gross At Carrying Value RealEstateGrossAtCarryingValue	7355079000	USD
CY2019Q4	us-gaap	Real Estate Gross At Carrying Value RealEstateGrossAtCarryingValue	8784567000	USD
CY2018Q4	us-gaap	Real Estate Gross At Carrying Value RealEstateGrossAtCarryingValue	8513935000	USD
CY2020Q4	srt	Real Estate Federal Income Tax Basis RealEstateFederalIncomeTaxBasis	9700000000	USD
CY2019Q4	us-gaap	Real Estate Accumulated Depreciation RealEstateAccumulatedDepreciation	2060560000	USD
CY2018Q4	us-gaap	Real Estate Accumulated Depreciation RealEstateAccumulatedDepreciation	2099137000	USD
CY2017Q4	us-gaap	Real Estate Accumulated Depreciation RealEstateAccumulatedDepreciation	2300116000	USD
CY2020	us-gaap	Sec Schedule Iii Real Estate Accumulated Depreciation Depreciation Expense SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense	270843000	USD
CY2019	us-gaap	Sec Schedule Iii Real Estate Accumulated Depreciation Depreciation Expense SECScheduleIIIRealEstateAccumulatedDepreciationDepreciationExpense	222867000	USD
CY2020	slg	Real Estate Accumulated Depreciation Real Estate Sold Retired Or Deconsolidated RealEstateAccumulatedDepreciationRealEstateSoldRetiredOrDeconsolidated	375326000	USD
CY2019	slg	Real Estate Accumulated Depreciation Real Estate Sold Retired Or Deconsolidated RealEstateAccumulatedDepreciationRealEstateSoldRetiredOrDeconsolidated	261444000	USD
CY2018	slg	Real Estate Accumulated Depreciation Real Estate Sold Retired Or Deconsolidated RealEstateAccumulatedDepreciationRealEstateSoldRetiredOrDeconsolidated	446012000	USD
CY2020Q4	us-gaap	Real Estate Accumulated Depreciation RealEstateAccumulatedDepreciation	1956077000	USD
CY2019Q4	us-gaap	Real Estate Accumulated Depreciation RealEstateAccumulatedDepreciation	2060560000	USD
CY2018Q4	us-gaap	Real Estate Accumulated Depreciation RealEstateAccumulatedDepreciation	2099137000	USD

Files In Submission

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0001040971-21-000007-index-headers.html	Edgar Link	pending
0001040971-21-000007-index.html	Edgar Link	pending
0001040971-21-000007.txt	Edgar Link	pending
0001040971-21-000007-xbrl.zip	Edgar Link	pending
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slg-20201231_cal.xml	Edgar Link	unprocessable
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slg-20201231_htm.xml	Edgar Link	completed
slg-20201231_lab.xml	Edgar Link	unprocessable
slg-20201231_pre.xml	Edgar Link	unprocessable

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$SLG
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2019 Q4 Form 10-K Financial Statement

#000104097121000007 Filed on February 26, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SLG SL Green Realty Corp Stock $slg

2019 Q4 Form 10-K Financial Statement

#000104097121000007 Filed on February 26, 2021

Income Statement

Balance Sheet

Cashflow Statement

Facts In Submission

Files In Submission

$SLG
SL Green Realty Corp Stock $slg