Disclosure of Compensation Related Costs, Share-based Payments [Abstract] Schedule of weighted average assumptions used to estimate the grant date fair value of options granted Schedule of Share-based Payment Award, Stock Options, Valuation Assumptions [Table Text Block] Summary of the status of stock options and changes during the period Share-based Compensation, Stock Options, Activity [Table Text Block] Summary of restricted stock and charges during the period Schedule of Share-based Compensation, Restricted Stock and Restricted Stock Units Activity [Table Text Block] Equity Method Investments and Joint Ventures [Abstract] Schedule of Equity Method Investments [Table] Schedule of Equity Method Investments [Table] Related Party [Axis] Related Party [Axis] Related Party [Domain] Related Party [Domain] Joint venture Corporate Joint Venture [Member] Investment in Unconsolidated Joint Ventures Schedule of Equity Method Investments [Line Items] Management fees, base revenue Management Fees, Base Revenue Assets (1) Equity Method Investment, Summarized Financial Information, Assets [Abstract] Commercial real estate property, net Real Estate Investment Property, Net Cash and cash equivalents Cash and Cash Equivalents, at Carrying Value Tenant and other receivables, related party receivables, and deferred rents receivable, net of allowance Accounts and Notes Receivable, Net Debt and preferred equity investments, net Mortgage Loans On Real Estate Commercial And Consumer And Equity Method Investments Net The balance represents the amount of loans that are secured by real estate mortgages, offset by any reserve to cover probable credit losses on the loan portfolio and deduction of deferred fees, unamortized costs, premiums and discounts from the face amounts. Included in this account is investment in unconsolidated joint venture which reflects the carrying amount on the entity's balance sheet of its investment in common stock of an equity method investee. This is not an indicator of the fair value of the investment, rather it is the initial cost adjusted for the entity's share of earnings and losses of the investee, adjusted for any distributions (dividends) and other than temporary impairment (OTTI) losses recognized. Other assets Other Assets Total assets Equity Method Investment, Summarized Financial Information, Assets Liabilities and equity (1) Equity Method Investment, Summarized Financial Information, Liabilities and Equity [Abstract] Mortgages and other loans payable, net Secured Debt Deferred revenue/gain Deferred Revenue Other liabilities Other Liabilities Members' equity Equity Method Investment Summarized Financial Information, Equity Total liabilities and members' equity Equity Method Investment, Summarized Financial Information, Liabilities and Equity Company's investments in unconsolidated joint ventures Equity Method Investments Combined statements of income for the unconsolidated joint ventures Equity Method Investment, Summarized Financial Information, Income Statement [Abstract] Total revenues Equity Method Investment, Summarized Financial Information, Revenue Operating expenses Costs and Expenses Ground rent Direct Costs of Leased and Rented Property or Equipment Real estate taxes Real Estate Tax Expense Interest expense, net of interest income Interest Expense, Net Amount of interest expense paid, net of interest income earned by the entity, during the period. Amortization of deferred financing costs Amortization of Debt Issuance Costs Transaction related costs Transaction Related Costs This Element represents the transaction related costs during the period. Depreciation and amortization Depreciation, Depletion and Amortization, Nonproduction Total expenses Total Costs and Expenses Including Nonoperating Income (Expense) This element represents the total of the costs related to real estate revenues, including management, leasing, and development services and income (expense) from ancillary business-related activities. Net (loss) income before gain on sale (1) Equity Method Investment, Summarized Financial Information, Net Income (Loss) Company's equity in net income from unconsolidated joint ventures (1) Income (Loss) from Equity Method Investments Noncontrolling Interest [Abstract] Schedule of Preferred Units [Table] Schedule of Preferred Units [Table] Consolidated Entities [Axis] Consolidated Entities [Axis] Consolidated Entities [Domain] Consolidated Entities [Domain] SL Green Operating Partnership Subsidiaries [Member] Class of Stock [Axis] Class of Stock [Axis] Class of Stock [Domain] Class of Stock [Domain] Preferred Units Preferred Stock [Member] Preferred Units [Line Items] Preferred Units [Line Items] Rollforward Analysis of Preferred Unit Activity Rollforward Analysis of Preferred Unit Activity [Roll Forward] Rollforward Analysis of Preferred Unit Activity [Roll Forward] Balance at beginning of period Noncontrolling Interest in Preferred Unit Holders Issuance of preferred units Noncontrolling Interest, Increase from Subsidiary Equity Issuance Redemption of preferred units Noncontrolling Interest, Decrease from Redemptions or Purchase of Interests Balance at end of period Debt Disclosure [Abstract] Interest expense Interest Income (Expense), Net [Abstract] Interest expense before capitalized interest Interest Expense Interest capitalized Capitalized Interest Costs, Including Allowance for Funds Used During Construction Interest income Interest Income, Operating Interest expense, net Interest Income (Expense), Net Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Commitments and Contingencies Disclosure [Text Block] Counterparty Name [Axis] Counterparty Name [Axis] Counterparty Name [Domain] Counterparty Name [Domain] Allianz Real Estate Allianz Real Estate [Member] Allianz Real Estate [Member] Mortgage Loans on Real Estate, Loan Type [Axis] Mortgage Loans on Real Estate, Loan Type [Axis] Mortgage Loans on Real Estate, Loan Type [Domain] Mortgage Loans on Real Estate, Loan Type [Domain] Mezzanine Loan Mezzanine Loan [Member] Mezzanine Loan [Member] Real Estate by Location [Axis] Real Estate by Location [Axis] Represents details pertaining to the locations of real estate properties of the entity. Real Estate by Location [Domain] Real Estate by Location [Domain] Identifies real estate properties of the entity by location. 21 East 66th Street East 21 Street 66 [Member] Represents the information pertaining to 21 East 66th Street, a joint venture property of the entity. Disposal Group Name [Axis] Disposal Group Name [Axis] Disposal Group Name [Domain] Disposal Group Name [Domain] East 400 Street 57 East 400 Street 57 [Member] Represents information pertaining to 400 East 57th Street, a property owned by the entity. Geographical [Axis] Geographical [Axis] Geographical [Domain] Geographical [Domain] 100 Park Avenue Park Avenue, 100 [Member] Represents the information pertaining to 100 Park Avenue, a joint venture property of the entity. 717 Fifth Avenue Fifth Avenue, 717 [Member] Represents the information pertaining to 717 Fifth Avenue, a joint venture property of the entity. 800 Third Avenue Third Avenue, 800 [Member] Represents the information pertaining to 800 Third Avenue, a joint venture property of the entity. 1745 Broadway Broadway, 1745 [Member] Represents the information pertaining to 1745 Broadway, a joint venture property of the entity. Jericho Plaza Jericho Plaza 1 and 2 [Member] Represents the information pertaining to 1 and 2 Jericho Plaza, a joint venture property of the entity. 11 West 34th Street West 11 Street 34 [Member] Represents the information pertaining to 11 West 34th Street, a joint venture property of the entity. 3 Columbus Circle Columbus Circle, 3 [Member] Represents the information pertaining to 3 Columbus Circle, a joint venture property of the entity. 280 Park Avenue Park Avenue, 280 [Member] Represents the information pertaining to 280 Park Avenue, a joint venture property of the entity. 1552-1560 Broadway Broadway 1552 to 1560 [Member] Represents the information pertaining to 1552-1560 Broadway, a joint venture property of the entity. 724 Fifth Avenue Fifth Avenue 724 [Member] Represents the information pertaining to 724 Fifth Avenue, a property acquired by the entity under the joint venture. 10 East 53rd Street East 53rd Street 10 [Member] Represents information pertaining to 10 East 53rd Street, a joint venture property of the entity. 521 Fifth Avenue Fifth Avenue, 521 [Member] Represents the information pertaining to 521 Fifth Avenue, a property owned by the entity. 650 Fifth Avenue 650 Fifth Avenue [Member] 650 Fifth Avenue [Member] 121 Greene Street Greene Street 121 [Member] Greene Street 121 [Member] 175-225 Third Street Brooklyn, New York Third Street 175-225 [Member] Third Street 175-225 [Member] 55 West 46th Street West 46th Street 55 [Member] West 46th Street 55 [Member] Stonehenge Portfolio Stonehenge Properties [Member] Represents the information pertaining to Stonehenge Properties. 131-137 Spring Street Spring Street 131 to 137 [Member] Represents information pertaining to property located at 131-137 Spring Street, owned by the entity. 605 West 42nd Street 605 West 42nd Street [Member] 605 West 42nd Street [Member] 11 Madison Avenue 11 Madison Ave [Member] 11 Madison Ave [Member] 333 East 22nd St 333 East 22nd St [Member] 333 East 22nd St [Member] 1552 Broadway Broadway 1552 [Member] Represents information pertaining to 1552 Broadway, a joint venture property of the entity. One Vanderbilt One Vanderbilt [Member] One Vanderbilt [Member] Worldwide Plaza Worldwide Plaza [Member] Worldwide Plaza [Member] 1515 Broadway Broadway, 1515 [Member] Represents the information pertaining to 1515 Broadway, a property owned by the entity. 919 Third Avenue Third Avenue, 919 [Member] Represents the information pertaining to 919 Third Avenue, a property owned by the entity. Real Estate, Type of Property [Axis] Real Estate, Type of Property [Axis] Real Estate, Property Type [Domain] Real Estate [Domain] Three Retail and Two Residential Units Three Retail and Two Residential Units [Member] Three Retail and Two Residential Units [Member] Three Residential Units Three Residential Units [Member] Three Residential Units [Member] General information on each joint venture Net equity investment in VIEs in which the entity is not primary beneficiary Variable Interest Entity Not Primary Beneficiary, Investment Represents the amount of equity investment in variable interest entities (VIEs) in which the entity is not a primary beneficiary. Ownership Interest Equity Method Investment, Ownership Percentage Economic Interest (as a percent) Equity Method Investment, Economic Interest Percentage The percentage of economic interest in the investee accounted for under the equity method of accounting. Unaudited Approximate Square Feet (sqft) Area of Real Estate Property Acquisition Price Equity Method Investment, Aggregate Cost Number of stores Number of Stores Number of residential units Number Of Residential Units Number Of Residential Units Ownership percentage in disposed asset Disposal Group Including Discontinued Operation, Ownership Percentage in Disposed Asset Disposal Group Including Discontinued Operation, Ownership Percentage in Disposed Asset Cumulative effect on retained earnings Cumulative Effect on Retained Earnings, Net of Tax Aggregate equity committed by partners Investment in Joint Venture, Aggregate Equity Committed by Partner Investment in Joint Venture, Aggregate Equity Committed by Partner Maximum ownership percentage of partners Investment in Joint Venture, Aggregate Maximum Ownership Percentage Investment in Joint Venture, Aggregate Maximum Ownership Percentage Partners' ownership percentage Investment in Joint Venture, Partners' Ownership Percentage Investment in Joint Venture, Partners' Ownership Percentage Equity method investment, amount sold Equity Method Investment, Amount Sold Purchase price and other fair value adjustments Purchase Price Fair Value Adjustment Gross The impact of fair value adjustments on purchase price and it's impact on net income or loss for the period, gross. Stockholders' Equity Note [Abstract] Stockholders Equity [Table] Stockholders Equity [Table] Disclosure of information pertaining to changes in stockholders' equity during the period. Award Type [Axis] Award Type [Axis] Equity Award [Domain] Equity Award [Domain] Common Stock Common Stock [Member] Stockholders' Equity Stockholders Equity [Line Items] -- None. No documentation exists for this element. -- Earnings Per Share Earnings Per Share [Abstract] Numerator Net Income (Loss) Attributable to Parent [Abstract] Basic Earnings: Net Income (Loss) Available to Common Stockholders, Basic [Abstract] Income attributable to SL Green common stockholders Net Income (Loss) Available to Common Stockholders, Basic Effect of Dilutive Securities: Dilutive Securities, Effect on Basic Earnings Per Share [Abstract] Redemption of units to common shares Dilutive Securities, Effect on Basic Earnings Per Share, Dilutive Convertible Securities Diluted Earnings: Net Income (Loss) Available to Common Stockholders, Diluted [Abstract] Income attributable to SL Green common stockholders Net Income (Loss) Available to Common Stockholders, Diluted Denominator Weighted Average Number of Shares Outstanding, Diluted [Abstract] Basic Shares: Weighted Average Number of Shares Outstanding, Basic [Abstract] Weighted average common shares outstanding (shares) Weighted Average Number of Shares Outstanding, Basic Effect of Dilutive Securities: Incremental Weighted Average Shares Attributable to Dilutive Effect [Abstract] Operating Partnership units redeemable for common shares (shares) Incremental Common Shares, Attributable to Redemption of Units to Common Shares Additional shares included in the calculation of diluted EPS as a result of the potentially dilutive effect of the redemption of units to common shares. Stock-based compensation plans (shares) Incremental Common Shares Attributable to Dilutive Effect of Share-based Payment Arrangements Diluted weighted average common stock outstanding (shares) Weighted Average Number of Shares Outstanding, Diluted Common stock shares excluded from the diluted shares outstanding (shares) Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount Equity [Abstract] Accumulated Other Comprehensive Income Stockholders' Equity Note Disclosure [Text Block] Investments in Unconsolidated Joint Ventures Equity Method Investments and Joint Ventures Disclosure [Text Block] Noncontrolling Interests on the Company's Consolidated Financial Statements Noncontrolling Interest Disclosure [Text Block] Mortgages and Other Loans Payable -- None. No documentation exists for this element. -- Schedule of first mortgages and other loans payable collateralized by the respective properties and assignment of leases Mortgage and Other Loans Payable [Table Text Block] Tabular disclosure of the information pertaining to mortgage and other loans payable of the entity. The disclosure may include but is not limited to identification of terms, features, collateral requirements and other information necessary to a fair presentation. Derivative Instruments and Hedging Activities Disclosure [Abstract] Schedule of notional and fair value of derivative financial instruments and foreign currency hedges Schedule of Derivative Instruments [Table Text Block] Schedule of effect of derivative financial instruments on consolidated statements of income Derivative Instruments, Gain (Loss) [Table Text Block] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Schedule of Share-based Compensation Arrangements by Share-based Payment Award [Table] Stock options Employee Stock Option [Member] Restricted Stock Awards Restricted Stock Awards [Member] Represents the restricted stock awards granted by the entity. Restricted stock are shares of stock for which sale is contractually or governmentally restricted for a given period of time. Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Share-based Compensation Arrangement by Share-based Payment Award [Line Items] Shares of common stock available for issuance (shares) Share-based Compensation Arrangement by Share-based Payment Award, Number of Shares Available for Grant Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions and Methodology [Abstract] Dividend yield (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Dividend Rate Expected life of option (in years) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Term Risk-free interest rate (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Risk Free Interest Rate Expected stock price volatility (as a percent) Share-based Compensation Arrangement by Share-based Payment Award, Fair Value Assumptions, Expected Volatility Rate Options Outstanding Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward] Balance at beginning of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Grants in Period, Net of Forfeitures Exercised (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercises in Period Lapsed or cancelled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period Balance at end of period (in shares) Options exercisable at end of period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Number Total fair value of options granted during the period Share Based Compensation Arrangement by Share Based Payment Award, Grants in Period Fair Value Represents the weighted average fair value of awards granted during the period. Weighted Average Exercise Price Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Exercise Price [Roll Forward] Share-based Compensation Arrangement by Share-based Payment Award, Options, Weighted Average Exercise Price [Roll Forward] Balance at beginning of year (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price Granted (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Grants in Period, Weighted Average Exercise Price Exercised (in dollars per share) Share-based Compensation Arrangements by Share-based Payment Award, Options, Exercises in Period, Weighted Average Exercise Price Lapsed or cancelled (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Forfeitures and Expirations in Period, Weighted Average Exercise Price Balance at end of period (in dollars per share) Options exercisable at end of period (in dollars per share) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Exercise Price Summary of restricted stock Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward] Balance at beginning of year (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number Granted (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Grants in Period Cancelled (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Forfeited in Period Balance at end of period (in shares) Vested during the period (in shares) Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period Statement of Financial Position [Abstract] Statement [Table] Statement [Table] Statement Statement [Line Items] Assets Assets [Abstract] Commercial real estate properties, at cost: Real Estate Investment Property, at Cost [Abstract] Land and land interests Land Building and improvements Investment Building and Building Improvements Building leasehold and improvements Building Leasehold Improvements, Gross Carrying amount at the balance sheet date of long-lived, depreciable asset that is an addition or improvement to assets held under lease arrangement as well as the initial investment in a leasehold interest. Properties under capital lease Capital Leased Assets, Gross Total commercial real estate properties, at cost Real Estate Investment Property, at Cost Less: accumulated depreciation Real Estate Investment Property, Accumulated Depreciation Total commercial real estate properties, net Assets held for sale Disposal Group, Including Discontinued Operation, Assets Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents Restricted cash Restricted Cash and Cash Equivalents Investments in marketable securities Marketable Securities Tenant and other receivables, net of allowance of $18,363 and $18,637 in 2018 and 2017, respectively Related party receivables Due from Related Parties Deferred rents receivable, net of allowance of $16,897and $17,207 in 2018 and 2017, respectively Deferred Rent Receivables, Net Debt and preferred equity investments, net of discounts and deferred origination fees of $24,998 and $25,507 in 2018 and 2017, respectively Mortgage Loans on Real Estate, Commercial and Consumer, Net Notes receivable Loans and Leases Receivable, Gross Investments in unconsolidated joint ventures Deferred costs, net Deferred Costs Total assets Assets Liabilities Liabilities [Abstract] Revolving credit facility, net Long-term Line of Credit Unsecured term loan, net Senior Notes Unsecured notes, net Unsecured Debt Accrued interest payable Accrued Interest Payable and Other Represents accrued interest and fair value of hedges entered into by the Entity. Accounts payable and accrued expenses Accounts Payable and Accrued Liabilities Deferred revenue Capital lease obligations Capital Lease Obligations Deferred land leases payable Deferred Rent Credit Dividend and distributions payable Dividends Payable Security deposits Security Deposit Liability Liabilities related to assets held for sale Disposal Group, Including Discontinued Operation, Liabilities Junior subordinated deferrable interest debentures held by trusts that issued trust preferred securities Junior Subordinated Debenture Owed to Unconsolidated Subsidiary Trust Total liabilities Liabilities Commitments and contingencies Commitments and Contingencies Noncontrolling interests in Operating Partnership Noncontrolling Interest in Operating Partnerships Limited partner interests in SLGOP (4,715 and 4,453 limited partner common units outstanding at March 31, 2018 and December 31, 2017, respectively) Limited Partners' Capital Account Preferred units Temporary Equity, Carrying Amount, Attributable to Parent Equity Stockholders Equity Including Portion Attributable to Noncontrolling Interest in Other Partnership [Abstract] -- None. No documentation exists for this element. -- Series I Preferred Stock, $0.01 par value, $25.00 liquidation preference, 9,200 issued and outstanding at both March 31, 2018 and December 31, 2017 Preferred Stock, Value, Issued Common stock, $0.01 par value, 160,000 shares authorized and 90,190 and 93,858 issued and outstanding at March 31, 2018 and December 31, 2017, respectively (including 1,055 shares held in treasury at March 31, 2018 and December 31, 2017) Common Stock, Value, Issued Additional paid-in-capital Additional Paid in Capital Treasury stock at cost Treasury Stock, Value Accumulated other comprehensive income Accumulated Other Comprehensive Income (Loss), Net of Tax Retained earnings Retained Earnings (Accumulated Deficit) Total SL Green stockholders' equity Stockholders' Equity Attributable to Parent Noncontrolling interests in other partnerships Other Noncontrolling Interests Total equity Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest SL Green stockholders equity: Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest [Abstract] Series I Preferred Units, $25.00 liquidation preference, 9,200 issued and outstanding at both March 31, 2018 and December 31, 2017 Preferred Units, Preferred Partners' Capital Accounts SL Green partners' capital (939 and 973 general partner common units and 88,196 and 91,831 limited partner common units outstanding at March 31, 2018 and December 31, 2017, respectively) General And Limited Partners Capital Account General And Limited Partners Capital Account Total SLGOP partners' capital Partners' Capital Noncontrolling interests in other partnerships Partners' Capital Attributable to Noncontrolling Interest Total capital Partners' Capital, Including Portion Attributable to Noncontrolling Interest Total liabilities and equity/capital Liabilities and Equity Share-based Compensation Disclosure of Compensation Related Costs, Share-based Payments [Text Block] Schedule of Long-term Debt Instruments [Table] Schedule of Long-term Debt Instruments [Table] Debt Instrument [Axis] Debt Instrument [Axis] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] Mezzanine Loan, Initial Maturity October 2022 [Member] Mezzanine Loan, Initial Maturity October 2022 [Member] Mezzanine Loan, Initial Maturity October 2022 [Member] Secured Debt, Initial Maturity November 2017 [Member] Secured Debt, Initial Maturity November 2017 [Member] Secured Debt, Initial Maturity November 2017 [Member] Secured Debt, Initial Maturity February 2027 [Member] Secured Debt, Initial Maturity February 2027 [Member] Secured Debt, Initial Maturity February 2027 [Member] Subsequent Event Type [Axis] Subsequent Event Type [Axis] Subsequent Event Type [Domain] Subsequent Event Type [Domain] Subsequent Event Subsequent Event [Member] 21 East 66th Street 1745 Broadway 175-225 Third Street Brooklyn, New York Jericho Plaza 1552 Broadway 280 Park Avenue 11 West 34th Street Long-term Debt, Type [Axis] Long-term Debt, Type [Axis] Long-term Debt, Type [Domain] Long-term Debt, Type [Domain] Mortgage loan Mortgages [Member] Mezzanine loans Mezzanine Loans on Real Estate [Member] Represents the mezzanine loans on real estate properties. Construction Loans Construction Loans [Member] Debt Instrument [Line Items] Interest rate, fixed rate debt (as a percent) Long-term Debt, Percentage Bearing Fixed Interest, Percentage Rate Interest rate, floating rate debt (as a percent) Long-term Debt, Percentage Bearing Variable Interest, Percentage Rate Total fixed rate debt Secured Debt, Bearing Fixed Interest, Amount The portion of the carrying amount of long-term secured loans outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate. Total floating rate debt Secured Debt, Bearing Variable Interest, Amount The portion of the carrying amount of long-term secured loans outstanding as of the balance sheet date, including current maturities, which accrues interest at a rate subject to change from time to time. Extension option exercised,term Debt Instrument, Extension Option Exercised, Term Debt Instrument, Extension Option Exercised, Term Total fixed rate and floating rate debt Secured Debt and Other Loans, Payable Represents the carrying value as of the balance sheet date, including the current and noncurrent portions, of collateralized debt obligations and other loans payable. Deferred financing costs, net Debt Issuance Costs, Net Total joint venture mortgages and other loans payable, net Secured Debt and Other Loans, Payable, Net Secured Debt and Other Loans, Payable, Net Committed amount Debt Instrument, Committed Amount Represents the maximum committed amount of the debt instrument. Unused borrowing capacity, amount Debt Instrument, Unused Borrowing Capacity, Amount Long-term debt, carrying value Long-term Debt Unfunded amount Debt Instrument, Unfunded Amount Debt Instrument, Unfunded Amount Term (in Years) Debt Instrument, Term Face amount of loan Debt Instrument, Face Amount Maximum facility capacity Line of Credit Facility, Maximum Borrowing Capacity Credit facility, interest rate (as a percent) Debt Instrument, Basis Spread on Variable Rate Number of extension options Debt Instrument, Number of Extension Options Debt Instrument, Number of Extension Options Period of extension options Debt Instrument, Period of Extension Option Debt Instrument, Period of Extension Option Schedule of senior unsecured notes and other related disclosures by scheduled maturity date Schedule of Long-term Debt Instruments [Table Text Block] Schedule of combined aggregate principal maturities Schedule of Maturities of Long-term Debt [Table Text Block] Schedule of consolidated interest expense, excluding capitalized interest Interest Income and Interest Expense Disclosure [Table Text Block] Plan Name [Axis] Plan Name [Axis] Plan Name [Domain] Plan Name [Domain] Third Amendment and Restated 2005 Stock Option and Incentive Plan Third Amendment and Restated 2005 Stock Option and Incentive Plan [Member] Third Amendment and Restated 2005 Stock Option and Incentive Plan [Member] Stock options, stock appreciation rights and other awards Stock Options Stock Appreciation Rights and Other Awards [Member] Represents the stock options, stock appreciation rights and other awards granted by the entity. Thes do not deliver full value and have an expiration date. All other awards Other Awards [Member] Represents awards granted by the entity that deliver the full value of the award upon vesting. 2014 Outperformance Plan Long Term Outperformance Compensation Program 2014 [Member] Long Term Outperformance Compensation Program 2014 [Member] Deferred Stock Compensation Plan for Directors Deferred Stock Compensation Plan for Directors [Member] Represents the Deferred Stock Compensation Plan for Directors of the entity. Employee Stock Purchase Plan Employee Stock Purchase Plan [Member] Employee Stock Purchase Plan [Member] Class O LTIP Units [Member] Class O LTIP Units [Member] Class O LTIP Units [Member] LTIP units Long Term Incentive Plan Units [Member] LTIP units as awarded by a company to its employees as a form of incentive compensation. Performance Shares Performance Shares [Member] Range [Axis] Range [Axis] Range [Domain] Range [Domain] Minimum Minimum [Member] Maximum Maximum [Member] Vesting [Axis] Vesting [Axis] Vesting [Domain] Vesting [Domain] Vesting on August 31, 2017 Share-based Compensation Award, Tranche Three [Member] Vesting on August 31, 2018 Share-based Compensation Award, Tranche Four [Member] Share-based Compensation Award, Tranche Four [Member] Maximum fungible units that may be granted (in shares) Share Based Compensation Arrangement by Share Based Payment Award, Number of Fungible Units Authorized Represents the maximum number of fungible units authorized to be granted by the entity. Fungible units per share (in fungible units per share) Share Based Compensation Arrangement by Share Based Payment Award, Fungible Units Per Share Share Based Compensation Arrangement by Share Based Payment Award, Fungible Units Per Share Award expiration period (in years) Share-based Compensation Arrangement by Share-based Payment Award, Expiration Period Shares that may be issued if equal to fungible units (shares) (less than) Share Based Compensation Arrangement by Share Based Payment Award, Number of Shares to be Issued if Equal to Fungible Units Represents the number of shares that would be issued under the plan if shares issued is equal to fungible units; actual shares issued may be more or less depending on the type of awards issued and the ratio of fungible units to shares under each award. Fungible units Share-based Compensation Arrangement By Share-based Payment Award, Number Of Fungible Units Available For Grant Share-based Compensation Arrangement By Share-based Payment Award, Number Of Fungible Units Available For Grant Options vesting period (in years) Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Period Period of commencement of option vesting, from date of grant (in years) Share Based Compensation Arrangement by Share Based Payment Award, Period of Award Vesting Commencement Represents the period from the date of grant of the awards for the commencement of vesting of awards. Exercise price of options granted, low end of the range (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Lower Range Limit Exercise price of options granted, high end of the range (in dollars per share) Share-based Compensation, Shares Authorized under Stock Option Plans, Exercise Price Range, Upper Range Limit Remaining weighted average contractual life of the options outstanding (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Remaining Contractual Term Remaining average contractual life of the options exercisable (in years) Share-based Compensation Arrangement by Share-based Payment Award, Options, Exercisable, Weighted Average Remaining Contractual Term Compensation expense Allocated Share-based Compensation Expense Total unrecognized compensation cost related to unvested stock awards Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized Weighted average period for recognition of compensation cost related to unvested stock awards (in years) Employee Service Share-based Compensation, Nonvested Awards, Compensation Cost Not yet Recognized, Period for Recognition Annual award vesting rate, low end of range (as a percent) Share Based Compensation Arrangement by Share Based Payment Award, Award Vesting Rate, Low End of Range Represents the low end of the range of annual vesting rates that occurs once performance criteria are reached. Annual award vesting rate, high end of range (as a percent) Share Based Compensation Arrangement by Share Based Payment Award, Award Vesting Rate, High End of Range Represents the low end of the range of annual vesting rates that occurs once performance criteria are reached. Fair value of restricted stock vested during the period Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Vested in Period, Fair Value Capitalized to assets associated with compensation expense related to our long-term compensation plans, restricted stock and stock options Employee Service Share-based Compensation, Allocation of Recognized Period Costs, Capitalized Amount Weighted average fair value of options granted during the period Share-based compensation Share-based Compensation LTIP units earned (in shares) Share Based Compensation, Arrangement by Share Based Payment Award, Equity Instruments Other than Options, Awards Earned Represents the awards earned by all participants under the stock based compensation plans. Award period (in years) Share-based Compensation Arrangement by Share--based Payment Award, Stock Appreciation Period Share-based Compensation Arrangement by Share--based Payment Award, Stock Appreciation Period Maximum award to be earned, if performance reaches maximum threshold, first performance period Share Based Compensation Arrangement By Share Based Payment Award, Maximum Award To Be Earned, If Performance Reaches Maximum Threshold, First Performance Period Share Based Compensation Arrangement By Share Based Payment Award, Maximum Award To Be Earned, If Performance Reaches Maximum Threshold, First Performance Period Maximum award to be earned, if performance reaches maximum threshold, second performance period Share Based Compensation Arrangement By Share Based Payment Award, Maximum Award To Be Earned, If Performance Reaches Maximum Threshold, Second Performance Period Share Based Compensation Arrangement By Share Based Payment Award, Maximum Award To Be Earned, If Performance Reaches Maximum Threshold, Second Performance Period Percentage of units vested Share-based Compensation Arrangement by Share-based Payment Award, Award Vesting Rights, Percentage Maximum percentage of the annual retainer fee, chairman fees and meeting fees that may be deferred by non-employee directors (percent) Deferred Compensation Arrangement with Individual Maximum Percentage of the Compensation that May be Deferred Represents the maximum percentage of the compensation that may be deferred by employees of the entity under deferred compensation plans. Awards granted (in shares) Shares issued (in shares) Deferred Compensation Arrangement with Individual, Shares Issued Awards outstanding (in shares) Duration of each offering period starting the first day of each calendar quarter (in months) Share Based Compensation Arrangement by Share Based Payment Award, Duration of Offering Periods Represents the duration of each offering period during which the shares are offered for purchase under the stock-based compensation plan of the entity. Discount from market price Share-based Compensation Arrangement by Share-based Payment Award, Discount from Market Price, Offering Date Shares of common stock issued (shares) Common Stock, Shares Held in Employee Trust, Shares Share Based Compensation Arrangement by Share Based Payment Award, Preferred Unit Distributions as a Percentage of Common Unit Distributions Share Based Compensation Arrangement by Share Based Payment Award, Preferred Unit Distributions as a Percentage of Common Unit Distributions Share Based Compensation Arrangement by Share Based Payment Award, Preferred Unit Distributions as a Percentage of Common Unit Distributions Accounting Policies [Abstract] Schedule of Property, Plant and Equipment and Finite Lived Intangible Assets and Liabilities, by Major Class [Table] Schedule of Property, Plant and Equipment and Finite Lived Intangible Assets and Liabilities, by Major Class [Table] Table of long-lived, physical assets and finite lived intangible assets and liabilities that are used in the normal conduct of business to produce goods and services and which are not intended for resale. Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Axis] Property, Plant and Equipment, Type [Domain] Property, Plant and Equipment, Type [Domain] Building Building [Member] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets by Major Class [Axis] Finite-Lived Intangible Assets, Major Class Name [Domain] Finite-Lived Intangible Assets, Major Class Name [Domain] Above-market leases Above Market Leases [Member] Below-market leases Leases, Below Market [Member] Leases, Below Market [Member] In-place leases In Place Leases [Member] Represents information pertaining to in-place leases. Investment in Commercial Real Estate Properties Property, Plant and Equipment [Line Items] Depreciable real estate reserves Depreciable Real Estate Reserves, Effect on Earnings Depreciable Real Estate Reserves, Effect on Earnings Estimated useful life (in years) Property, Plant and Equipment, Useful Life Estimated useful life of other intangible assets (in years) Finite-Lived Intangible Asset, Useful Life Rental revenue from amortization of acquired leases Rental Revenue Increase (Decrease) Acquired Lease Amortization Represents the increase (decrease) in rental revenue during the period resulting from the net amortization of acquired above-market and below-market leases. Reduction in interest expense from amortization of above-market rate mortgages Interest Expense Increase (Decrease) Assumed Above Market Rate Mortgage Amortization Represents the increase (decrease) in interest expense during the period resulting from the amortization of assumed above-market rate mortgages. Identified intangible assets (included in other assets): Finitely Lived Intangible Assets [Abstract] -- None. No documentation exists for this element. -- Gross amount Finite-Lived Intangible Assets, Gross Accumulated amortization Finite-Lived Intangible Assets, Accumulated Amortization Net Finite-Lived Intangible Assets, Net Identified intangible liabilities (included in deferred revenue): Finite Lived Intangible Liabilities [Abstract] -- None. No documentation exists for this element. -- Gross amount Finite Lived Intangible Liabilities, Gross Represents the gross carrying amounts before accumulated amortization as of the balance sheet date of all intangible liabilities having statutory or estimated useful lives. Accumulated amortization Finite Lived Intangible Liabilities, Accumulated Amortization Represents the accumulated amount of amortization of a major finite-lived intangible liability class. Net Finite Lived Intangible Liabilities, Net Represents the sum of gross carrying value of a major finite-lived intangible liability class, less accumulated amortization. Net intangible assets reclassed to assets held for sale Net Intangible Assets Transferred to Assets Held for Sale Net Intangible Assets Transferred to Assets Held for Sale Net intangible liabilities reclassed to liabilities relates to assets held for sale Net Intangible Liabilities Transferred to Liabilities Related to Assets Held for Sale Net Intangible Liabilities Transferred to Liabilities Related to Assets Held for Sale Segment Reporting [Abstract] Segment Information Segment Reporting Disclosure [Text Block] Fair Value Disclosures [Abstract] Fair Value Measurements Fair Value Disclosures [Text Block] Principles of Consolidation Consolidation, Policy [Policy Text Block] Investment in Commercial Real Estate Properties Investment in Real Estate [Policy Text Block] Disclosure of accounting policy for investments in real estate properties. Fair Value Measurements Fair Value of Financial Instruments, Policy [Policy Text Block] Investment in Marketable Securities Marketable Securities, Policy [Policy Text Block] Investments in Unconsolidated Joint Ventures Equity Method Investments [Policy Text Block] Reserve for Possible Credit Losses Financing Receivable, Allowance for Credit Losses, Policy or Methodology Change [Policy Text Block] Income Taxes Income Tax, Policy [Policy Text Block] Use of Estimates Use of Estimates, Policy [Policy Text Block] Concentrations of Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Reclassification Reclassification, Policy [Policy Text Block] Accounting Standards Updates New Accounting Pronouncements, Policy [Policy Text Block] Income Statement [Abstract] Revenues Revenues [Abstract] Rental revenue, net Operating Leases, Income Statement, Minimum Lease Revenue Escalation and reimbursement Tenant Reimbursements Investment income Investment Income, Interest and Dividend Other income Other Income Total revenues Revenues Expenses Costs and Expenses [Abstract] Operating expenses, including related party expenses of $3,834 in 2018 and $4,173 in 2017. Transaction related costs Marketing, general and administrative Selling, General and Administrative Expense Income before equity in net income from unconsolidated joint ventures, equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities Income (Loss) from Continuing Operations before Equity Method Investments, Income Taxes, Noncontrolling Interest Equity in net income from unconsolidated joint ventures Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate Equity Method Investment, Realized Gain (Loss) on Disposal Gain on sale of real estate, net Gains (Losses) on Sales of Investment Real Estate Gain on sale of investment in marketable securities Marketable Securities, Gain (Loss) Net income Net Income (Loss), Including Portion Attributable to Noncontrolling Interest Net (income) loss attributable to noncontrolling interests: Net Income (Loss) Attributable to Noncontrolling Interest [Abstract] Noncontrolling interests in the Operating Partnership Noncontrolling Interest in Net Income (Loss) Operating Partnerships, Redeemable Noncontrolling interests in other partnerships Noncontrolling Interest in Net Income (Loss) Other Noncontrolling Interests, Redeemable Preferred units distributions Noncontrolling Interest in Net Income (Loss) Preferred Unit Holders, Redeemable Net income (loss) attributable to SL Green/SLGOP Net Income (Loss) Attributable to Parent Perpetual preferred stock dividends Dividends, Preferred Stock Perpetual preferred unit distributions Preferred Stock Dividends and Other Adjustments Net income attributable to SLGOP common unitholders Net Income (Loss) Allocated to, Common Unitholders This element represents amounts attributable to ROP common unitholders. Amounts attributable to SL Green common stockholders: Income Amounts Attributable to Parent, Disclosures [Abstract] Income before depreciable real estate reserves and gains on sale and fair value adjustments Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent Purchase price and other fair value adjustments Purchase Price Fair Value Adjustments Attributable to Parent The impact of fair value adjustments on purchase price and it's impact on net income or loss for the period attributable to parent. Equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate Gain (Loss) on Sale of Unconsolidated Joint Ventures or Real Estate Gain (Loss) on Sale of Unconsolidated Joint Ventures or Real Estate reflects the amount by which the consideration received exceeds (is exceeded by) the net carrying amount (reflecting previous provisions for loss on disposal, if any) of the disposal group. Gain on sale of real estate, net Gains (Losses) on Sales of Investment Real Estate, Attributable to Parent Gains (Losses) on Sales of Investment Real Estate, Attributable to Parent Depreciable real estate reserves Depreciable Real Estate Reserves, Effect on Earnings, Attributable to Parent Depreciable Real Estate Reserves, Effect on Earnings, Attributable to Parent Net income attributable to SL Green common stockholders Basic earnings per share: Earnings Per Share, Basic [Abstract] Income (loss) before depreciable real estate reserves and gains (losses) on sale (in dollars per share) Income (Loss) from Continuing Operations, Per Outstanding Limited Partnership Unit, Basic, Net of Tax Income (loss) before depreciable real estate reserves and gains (losses) on sale (in dollars per share) Income (Loss) from Continuing Operations, Per Basic Share Purchase price and other fair value adjustments (in dollars per share) Purchase Price Fair Value Adjustment, Per Basic Unit Purchase Price Fair Value Adjustment, Per Basic Unit Equity in net gain on sale of interest in unconsolidated joint venture/real estate (in dollars per share) Gain (Loss) on Sale of Unconsolidated Joint Ventures or Real Estate, Per Basic Share The amount of gain (loss) from sale of unconsolidated joint ventures or real estate per basic share. Gain on sale of real estate, net (in dollars per share) Gains (Losses) on Sales of Investment Real Estate, Per Basic Share Gains (Losses) on Sales of Investment Real Estate, Per Basic Share Depreciable real estate reserves (in dollars per share) Depreciable Real Estate Reserves, Effect on Earnings, Per Basic Share Depreciable Real Estate Reserves, Effect on Earnings, Per Basic Share Net income attributable to SL Green common stockholders (usd per share) Earnings Per Share, Basic Net income attributable to SLGOP common unitholders (usd per share) Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic, Net of Tax Diluted earnings per share: Earnings Per Share, Diluted [Abstract] Income (loss) before depreciable real estate reserves and gains (losses) on sale (in dollars per share) Income (Loss) from Continuing Operations, Net of Tax, Per Outstanding Limited Partnership Unit, Diluted Purchase price and other fair value adjustments (in dollars per share) Purchase Price Fair Value Adjustment, Per Diluted Unit Purchase Price Fair Value Adjustment, Per Diluted Unit Income (loss) before depreciable real estate reserves and gains (losses) on sale (in dollars per share) Income (Loss) from Continuing Operations, Per Diluted Share Equity in net gain on sale of interest in unconsolidated joint venture/real estate (in dollars per share) Gain (Loss) on Sale of Unconsolidated Joint Ventures or Real Estate, Per Diluted Share The amount of gain (loss) from sale of unconsolidated joint ventures or real estate per diluted share. Gain on sale of real estate (in dollars per share) Gains (Losses) on Sales of Investment Real Estate, Per Diluted Share Gains (Losses) on Sales of Investment Real Estate, Per Diluted Share Depreciable real estate reserves (in dollars per share) Depreciable Real Estate Reserves, Effect on Earnings, Per Diluted Share Depreciable Real Estate Reserves, Effect on Earnings, Per Diluted Share Net income attributable to SL Green common stockholders (usd per share) Earnings Per Share, Diluted Net income attributable to SLGOP common unitholders (usd per share) Net Income (Loss), Net of Tax, Per Outstanding Limited Partnership Unit, Diluted Dividends per share/unit (usd per share) Common Stock, Dividends, Per Share, Declared Basic weighted average common shares outstanding (in shares) Basic weighted average common units outstanding (in shares) Weighted Average Limited Partnership Units Outstanding, Basic Diluted weighted average common shares and common share equivalents outstanding (in shares) Diluted weighted average common units and common unit equivalents outstanding (in shares) Weighted Average Limited Partnership Units Outstanding, Diluted Summary of identified intangible assets (acquired above-market leases and in-place leases) and intangible liabilities (acquired below-market leases) Schedule of Intangible Assets and Liabilities [Table Text Block] Tabular disclosure of the aggregate amount of intangible assets and liabilities. Schedule of marketable securities Available-for-sale Securities [Table Text Block] Deferred Costs, Capitalized, Prepaid, and Other Assets Disclosure [Abstract] Schedule of components of deferred costs Schedule of Deferred Costs [Table Text Block] Tabular disclosure of the components of deferred costs. Series I Preferred Stock Series I Preferred Stock [Member] Outstanding nonredeemable series I preferred stock or outstanding series I preferred stock. Classified within stockholders' equity if nonredeemable or redeemable solely at the option of the issuer. Classified within temporary equity if redemption is outside the control of the issuer. Dividend Reinvestment and Stock Purchase Plan (DRIP) Dividend Reinvestment and Stock Purchase Plan [Member] Represents the dividend reinvestment and stock purchase plan of the entity. Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Dividend rate preferred units (as a percent) Preferred Stock, Dividend Rate, Percentage Perpetual preferred stock, liquidation preference (in dollars per share) Preferred Stock, Liquidation Preference Per Share Perpetual preferred stock, annual dividends per share (in dollars per share) Preferred Stock, Dividend Rate, Per-Dollar-Amount Contributions of net proceeds from sale of preferred stock Proceeds from Issuance of Preferred Stock and Preference Stock Common stock, shares authorized (in shares) Common Stock, Shares Authorized Corporate Indebtedness Debt Disclosure [Text Block] Business Combinations [Abstract] Property Acquisitions Business Combination Disclosure [Text Block] Investments, Debt and Equity Securities [Abstract] Mortgage Loans on Real Estate Schedule [Table] Mortgage Loans on Real Estate Schedule [Table] Preferred Equity, April 2021 Preferred Equity, April 2021 [Member] Preferred Equity, April 2021 [Member] Preferred equity investments Preferred Equity Investments in Mortgage Loans [Member] Represents preferred equity investments in mortgage loans on real estate. Preferred equity investment Mortgage Loans on Real Estate [Line Items] Aggregate weighted average current yield (as a percent) Mortgage Loans on Real Estate, Interest Rate Future Funding Obligations Loans and Leases Receivable, Funding Obligation Loans and Leases Receivable, Funding Obligation Senior Financing Mortgage Loans on Real Estate, Senior Debt on Investment Amount as of the balance sheet date of debt which holds a position senior to the entity's investment in a mortgage loan on real estate. Carrying Value Schedule of debt and preferred equity book balance roll forward Schedule Of Debt And Preferred Equity Book Balance Roll Forward [Table Text Block] Schedule Of Debt And Preferred Equity Book Balance Roll Forward Summary of debt investments Schedule of Mortgage Loans on Real Estate [Table Text Block] Tabular disclosure of investments in mortgage loans on real estate. Summary of preferred equity investments Investments Classified by Contractual Maturity Date [Table Text Block] Significant Accounting Policies Significant Accounting Policies [Text Block] Concentration Risk [Table] Concentration Risk [Table] Adjustments for New Accounting Pronouncements [Axis] Adjustments for New Accounting Pronouncements [Axis] Type of Adoption [Domain] Type of Adoption [Domain] Accounting Standards Update 2017-05 Accounting Standards Update 2017-05 [Member] Accounting Standards Update 2017-05 [Member] Customer [Axis] Customer [Axis] Customer [Domain] Customer [Domain] Tenant 1 Tenant 1 [Member] Represents first tenant of the entity for which a concentration risk is disclosed. Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Axis] Concentration Risk Benchmark [Domain] Concentration Risk Benchmark [Domain] Annualized rent Annualized Rent [Member] Annualized rent, when it serves as a benchmark in a concentration of risk calculation. 1185 Avenue of the Americas Avenue of the Americas, 1185 [Member] Represents the information pertaining to 1185 Avenue of the Americas, a property owned by the entity. 420 Lexington Avenue Lexington Avenue, 420 [Member] Represents the information pertaining to 420 Lexington Avenue, a property owned by the entity. 1 Madison Ave 1 Madison Ave [Member] 1 Madison Ave [Member] Concentration Risk Type [Axis] Concentration Risk Type [Axis] Concentration Risk Type [Domain] Concentration Risk Type [Domain] Customer concentration Customer Concentration Risk [Member] Concentration of Credit Risk Concentration Risk [Line Items] Number of tenants (tenants) Number of Tenants Represents the number of tenants to whom the facility is leased. Percentage of concentration (percent) Concentration Risk, Percentage Maximum percentage of annualized rent for any one tenant not individually disclosed (percent) (more than) Concentration Risk Percentage Threshold Represents the maximum percentage of concentration risk that is not individually disclosed. Gain on disposal Total fixed rate Fixed Rate [Member] Fixed Rate [Member] Total floating rate Debt Investment with Floating Interest Rate [Member] Represents the debt investment in mortgage loans having a floating interest rate. Mezzanine/Jr. Mortgage Loan with an Initial Maturity Date of April 2017 Mortgage and Jr Mortgage Loan with an Initial Maturity Date of April 2017 [Member] Mortgage and Jr Mortgage Loan with an Initial Maturity Date of April 2017 [Member] Mortgage Loan, February 2019 Mortgage Loan With An Initial Maturity Date Of February 2019 [Member] Mortgage Loan With An Initial Maturity Date Of February 2019 [Member] Mortgage Loan, August 2019 Mortgage Loan with an Initial Maturity of August 2019 [Member] Mortgage Loan with an Initial Maturity of August 2019 [Member] Mezzanine Loan with an Initial Maturity Date of March 2020 Mezzanine Loan with an Initial Maturity Date of March 2020 [Member] Mezzanine Loan with an Initial Maturity Date of March 2020 [Member] Mezzanine Loan, September 2021 Mezzanine Loan with an Initial Maturity Date of September 2021 [Member] Mezzanine Loan with an Initial Maturity Date of September 2021 [Member] Mezzanine Loan with an Initial Maturity Date of April 2022 Mezzanine Loan with an Initial Maturity Date of April 2022 [Member] Mezzanine Loan with an Initial Maturity Date of April 2022 [Member] Mezzanine Loan, November 2023 Mezzanine Loan, with an Initial Maturity Date of November 2023 [Member] Mezzanine Loan, with an Initial Maturity Date of November 2023 [Member] Mezzanine Loan, with an Initial Maturity Date of June 2024 Mezzanine Loan with an Initial Maturity Date of June 2024 [Member] Mezzanine Loan with an Initial Maturity Date of June 2024 [Member] Mezzanine Loan, January 2025 Mezzanine Loan, with an Initial Maturity Date of January 2025 [Member] Mezzanine Loan, with an Initial Maturity Date of January 2025 [Member] Mezzanine Loan with an Initial Maturity Date of November 2026 Mezzanine Loan with an Initial Maturity Date of November 2026 [Member] Mezzanine Loan with an Initial Maturity Date of November 2026 Mezzanine Loan with an Initial Maturity Date of June 2027 Mezzanine Loan with an Initial Maturity Date of June 2027 [Member] Mezzanine Loan with an Initial Maturity Date of June 2027 [Member] Mezzanine Loan with an Initial Maturity Date of December 2017 Mezzanine Loan with an Initial Maturity Date of April 2018, 2 [Member] Mezzanine Loan with an Initial Maturity Date of April 2018, 2 [Member] Mezzanine Loan with an Initial Maturity Date of April 2018 Mezzanine Loan with an Initial Maturity Date of April 2018 [Member] Mezzanine Loan with an Initial Maturity Date of April 2018 [Member] Mezzanine Loan with an Initial Maturity Date of August 2018 Mezzanine Loan with an Initial Maturity Date of August 2018 [Member] Mezzanine Loan with an Initial Maturity Date of August 2018 [Member] Mortgage/Mezzanine Loan, with an Initial Maturity Date of August 2018 Mortgage/Mezzanine Loan, with an Initial Maturity Date of August 2018 [Member] Mortgage/Mezzanine Loan, with an Initial Maturity Date of August 2018 [Member] Mezzanine Loan With An Initial Maturity Date of August 2018, 2 Mezzanine Loan With An Initial Maturity Date of August 2018, 2 [Member] Mezzanine Loan With An Initial Maturity Date of August 2018, 2 [Member] Mortgage/Mezzanine Loan, September 2018 Mortgage/Mezzanine Loan with an Initial Maturity Date of September 2018 [Member] Mortgage/Mezzanine Loan with an Initial Maturity Date of September 2018 [Member] Mezzanine Loan with an Initial Maturity Date of September 2018 Mezzanine Loan with an Initial Maturity Date of September 2018 [Member] Mezzanine Loan with an Initial Maturity Date of September 2018 [Member] Mortgage/Mezzanine Loan with an Initial Maturity Date of October 2016 [Member] Mortgage/Mezzanine Loan with an Initial Maturity Date of October 2018 [Member] Mortgage/Mezzanine Loan with an Initial Maturity Date of October 2018 [Member] Mezzanine Loan with an Initial Maturity Date of October 2018 Mezzanine Loan with an Initial Maturity Date of October 2018 [Member] Mezzanine Loan with an Initial Maturity Date of October 2018 [Member] Mezzanine Loan with an Initial Maturity Date of December 2018 Mezzanine Loan with an Initial Maturity Date of December 2018 [Member] Mezzanine Loan with an Initial Maturity Date of December 2018 [Member] Mezzanine Loan with an Initial Maturity Date of December 2018, 2 Mezzanine Loan with an Initial Maturity Date of December 2018, 2 [Member] Mezzanine Loan with an Initial Maturity Date of December 2018, 2 [Member] Mezzanine Loan with an Initial Maturity Date of December 2018, 3 Mezzanine Loan with an Initial Maturity Date of December 2018, 3 [Member] Mezzanine Loan with an Initial Maturity Date of December 2018, 3 [Member] Mezzanine Loan with an Initial Maturity Date of December 2018, 4 Mezzanine Loan with an Initial Maturity Date of December 2018, 4 [Member] Mezzanine Loan with an Initial Maturity Date of December 2018, 4 [Member] Mezzanine Loan with an Initial Maturity Date of January 2019 Mezzanine Loan with an Initial Maturity Date of January 2019 [Member] Mezzanine Loan with an Initial Maturity Date of January 2019 [Member] Mezzanine Loan with an Initial Maturity of January 2019, 2 Mezzanine Loan with an Initial Maturity of January 2019, 3 [Member] Mezzanine Loan with an Initial Maturity of January 2019, 3 [Member] Mezzanine Loan with an Initial Maturity of March 2019 Mezzanine Loan with an Initial Maturity of March 2019 [Member] Mezzanine Loan with an Initial Maturity of March 2019 [Member] Mezzanine Loan with an Initial Maturity of March 2019, 2 [Member] Mezzanine Loan with an Initial Maturity of March 2019, 2 [Member] Mezzanine Loan with an Initial Maturity of March 2019, 2 [Member] Mezzanine Loan with an Initial Maturity Date of April 2019 Mezzanine Loan with an Initial Maturity Date of April 2019 [Member] Mezzanine Loan with an Initial Maturity Date of April 2019 [Member] Mezzanine Loan with an Initial Maturity Date of April 2019, 2 [Member] Mezzanine Loan with an Initial Maturity Date of April 2019, 2 [Member] Mezzanine Loan with an Initial Maturity Date of April 2019, 2 [Member] Mortgage/Jr Mortgage Participate Loan, Maturity Date of August 2019 Mortgage/Jr Mortgage Participate Loan, Maturity Date of August 2019 [Member] Mortgage/Jr Mortgage Participate Loan, Maturity Date of August 2019 [Member] Mezzanine Loan, Maturity of September 2019 Mezzanine Loan, Maturity of September 2019 [Member] Mezzanine Loan, Maturity of September 2019 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of September 2019 Mortgage/Mezzanine Loan with an Initial Maturity of September 2019 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of September 2019 [Member] Mezzanine Loan with an Initial Maturity of October 2019 [Member] Mezzanine Loan with an Initial Maturity of October 2019 [Member] Mezzanine Loan with an Initial Maturity of October 2019 [Member] Mortgage/Mezzanine Loan with an Initial Maturity Date of December 2019 [Member] Mortgage/Mezzanine Loan with an Initial Maturity Date of December 2019 [Member] Mortgage/Mezzanine Loan with an Initial Maturity Date of December 2019 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of January 2020 Mortgage/Mezzanine Loan with an Initial Maturity of January 2020 [Member] [Member] Mortgage/Mezzanine Loan with an Initial Maturity of January 2020 [Member] [Member] Mezzanine Loan with an Initial Maturity of January 2020 Mezzanine Loan with an Initial Maturity of January 2020 [Member] Mezzanine Loan with an Initial Maturity of January 2020 [Member] Mortgage Loan with an Initial Maturity of February 2020 [Member] Mortgage Loan with an Initial Maturity of February 2020 [Member] Mortgage Loan with an Initial Maturity of February 2020 [Member] Mezzanine Loan with an Initial Maturity of July 2020 [Member] Mezzanine Loan with an Initial Maturity of July 2020 [Member] Mezzanine Loan with an Initial Maturity of July 2020 [Member] Mezzanine Loan with an Initial Maturity of July 2020 [Domain] Mezzanine Loan with an Initial Maturity of November 2020 [Member] Mezzanine Loan with an Initial Maturity of November 2020 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of December 2020 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of December 2020 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of December 2020 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of December 2020, 2 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of December 2020, 2 [Member] Mortgage/Mezzanine Loan with an Initial Maturity of December 2020, 2 [Member] Jr Mortgage Participation/Mezzanine Loan with an Initial Maturity of July 2021 Jr Mortgage Participation/Mezzanine Loan with an Initial Maturity of July 2021 [Member] Jr Mortgage Participation/Mezzanine Loan with an Initial Maturity of July 2021 [Member] Mezzanine Loan with an Initial Maturity of August 2022 Mezzanine Loan With An Initial Maturity Of August 2022 [Member] Mezzanine Loan With An Initial Maturity Of August 2022 Mortgage/Mezzanine Loan repaid in June 2017 Mortgage/Mezzanine Loan repaid in February 2018 [Member] Mortgage/Mezzanine Loan repaid in February 2018 [Member] Mezzanine Loan Contributed for a Joint Venture Interest Mezzanine Loan repaid in February 2018 [Member] Mezzanine Loan repaid in February 2018 [Member] Debt Investments in Mortgage Loans Debt Investments in Mortgage Loans [Member] Represents debt investments in mortgage loans on real estate. Junior Mortgage Participation, Related To Mortgage Loan, February 2019 Junior Mortgage Participation, Related To Mortgage Loan, February 2019 [Member] Junior Mortgage Participation, Related To Mortgage Loan, February 2019 [Member] Mortgage Loans on Real Estate [Line Items] Debt Investments Held [Abstract] Debt Investments Held [Abstract] Debt Investments Held [Abstract] Carrying Value Interest Receivable Interest Receivable Loan acquired Receivable with Imputed Interest, Face Amount Discount amount Receivable with Imputed Interest, Discount Amount participated out Mortgage Loans on Real Estate Loan Value Represents the amount of loan participation on property mortgage. Organization, Consolidation and Presentation of Financial Statements [Abstract] Schedule of commercial office properties Schedule of Real Estate Properties [Table Text Block] Financial Instruments: Derivatives and Hedging Derivative Instruments and Hedging Activities Disclosure [Text Block] Debt and Preferred Equity Investments Investments in Debt and Marketable Equity Securities (and Certain Trading Assets) Disclosure [Text Block] Operating expenses, paid to related parties Affiliate Costs Fair value measurements, recurring and nonrecurring Fair Value Measurements, Recurring and Nonrecurring [Table Text Block] Fair value, by balance sheet grouping Fair Value, by Balance Sheet Grouping [Table Text Block] Class of Treasury Stock [Table] Class of Treasury Stock [Table] Share Repurchase Program [Axis] Share Repurchase Program [Axis] Share Repurchase Program [Domain] Share Repurchase Program [Domain] 2016 Repurchase Program 2016 Repurchase Program [Member] 2016 Repurchase Program [Member] Equity, Class of Treasury Stock [Line Items] Equity, Class of Treasury Stock [Line Items] Authorized capital stock (shares) Total Shares Authorized The maximum number of total capital shares permitted to be issued by an entity's charter and bylaws. Authorized shares, par value (in dollars per share) Total Par or Stated Value Per Share Face amount or stated value of capital stock per share; generally not indicative of the fair market value per share. Common stock, par value (in dollars per share) Common Stock, Par or Stated Value Per Share Excess stock, shares authorized (shares) Excess Stock, Shares Authorized Excess stock, par value (in dollars per share) Excess Stock, Par or Stated Value Per Share Face amount or stated value of excess stock per share, which is generally not indicative of the fair market value per share. Preferred stock, shares authorized (shares) Preferred Stock, Shares Authorized Preferred stock, par value (in dollars per share) Preferred Stock, Par or Stated Value Per Share Shares, outstanding (in shares) Shares, Outstanding Excess shares issued (shares) Excess Stock, Shares Issued Stock repurchase program, authorized amount Stock Repurchase Program, Authorized Amount Shares repurchased Stock Repurchased During Period, Shares Average price paid per share (in dollars per share) Treasury Stock Acquired, Average Cost Per Share Maximum approximate dollar value of shares that may yet be purchased under the plan Stock Repurchase Program, Remaining Authorized Repurchase Amount Stock repurchase program, authorized amount Stock Repurchase Program, Authorized Amount, Total Stock Repurchase Program, Authorized Amount, Total Repurchases of common stock (in shares) Treasury Stock, Shares, Acquired Credit Facility [Axis] Credit Facility [Axis] Credit Facility [Domain] Credit Facility [Domain] Revolving credit facility Revolving Credit Facility [Member] Term Loan B, Maturity November 21, 2024 Term Loan B, Maturity November 21, 2024 [Member] Term Loan B [Member] Revolving Credit Facility, Maturity March 31, 2022 Revolving Credit Facility, Maturity March 31, 2022 [Member] Revolving Credit Facility, Maturity March 31, 2022 [Member] Term loan Term Loan [Member] Represents the term loan of the reporting entity. 2012 Credit Facility Credit Facility 2012 [Member] Represents information pertaining to 2012 Credit Facility. Term Loan A, Maturity March 31, 2023 Term Loan A, Maturity March 31, 2023 [Member] Term Loan A [Member] Variable Rate [Axis] Variable Rate [Axis] Variable Rate [Domain] Variable Rate [Domain] LIBOR London Interbank Offered Rate (LIBOR) [Member] Line of Credit Line of Credit [Member] Corporate Indebtedness Credit facility, maximum borrowing capacity Number of extensions Line Of Credit Facility, Number Of Extensions Line Of Credit Facility, Number Of Extensions Term of extension Line Of Credit Facility, Term Of Extension Line Of Credit Facility, Term Of Extension Maximum borrowing capacity, optional expansion Line of Credit Facility, Optional Expansion, Maximum Borrowing Capacity The expanded maximum borrowing capacity available, which is subject to agreement with the entity. Interest rate added to base rate (as a percent) Facility fee (as a percent) Line of Credit Facility, Commitment Fee Percentage Letters of credit Letters of Credit Outstanding, Amount Outstanding under line of credit facility Ability to borrow under line of credit facility Line of Credit Facility, Remaining Borrowing Capacity Schedule of accumulated other comprehensive income (loss) Schedule of Accumulated Other Comprehensive Income (Loss) [Table Text Block] Investments Schedule [Abstract] Investment [Axis] Investment [Axis] Investment [Domain] Investment [Domain] Movement in Mortgage Loans on Real Estate [Roll Forward] Movement in Mortgage Loans on Real Estate [Roll Forward] Balance at beginning of period Mortgage Loans on Real Estate Originations/Accretion Mortgage Loans on Real Estate, New Mortgage Loans Redemptions/Sales/Syndications/Amortization Mortgage Loans on Real Estate, Amortization of Premium Balance at end of period Accumulated Other Comprehensive Income (Loss) [Table] Accumulated Other Comprehensive Income (Loss) [Table] Equity Components [Axis] Equity Components [Axis] Equity Component [Domain] Equity Component [Domain] Net unrealized (loss) gain on derivative instruments Accumulated Net Gain (Loss) from Cash Flow Hedges Attributable to Parent [Member] Net unrealized gain on marketable securities Accumulated Net Investment Gain (Loss) Attributable to Parent [Member] Accumulated Other Comprehensive Income AOCI Attributable to Parent [Member] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) [Line Items] Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward] Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward] Accumulated Other Comprehensive Income (Loss) of the Company [Roll Forward] Beginning Balance Other comprehensive (loss) income before reclassifications Other Comprehensive Income (Loss), before Reclassifications, Net of Tax Amounts reclassified from accumulated other comprehensive income Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax Ending Balance Deferred net losses from terminated hedges Other Comprehensive Income (Loss), Deferred Net Loss from Terminated Hedges Other Comprehensive Income (Loss), Deferred Net Loss from Terminated Hedges Derivative [Table] Derivative [Table] Derivative Instrument [Axis] Derivative Instrument [Axis] Derivative Contract Type [Domain] Derivative Contract [Domain] Interest Rate Swap Expiring in July 2023 Interest Rate Swap Expiring in July 2023 [Member] Interest Rate Swap Expiring in July 2023 [Member] Interest Rate Swap Expiring in July 2023 Interest Rate Swap Expiring in July 2023, 2 [Member] Interest Rate Swap Expiring in July 2023, 2 [Member] Interest Rate Cap Expiring September 2019 Interest Rate Cap Expiring September 2019 [Member] Interest Rate Cap Expiring September 2019 [Member] Interest Rate Swap Expiring November 2020 Interest Rate Swap Expiring November 2020 [Member] Interest Rate Swap Expiring November 2020 [Member] Interest Rate Swap Expiring November 2020, 2 Interest Rate Swap Expiring November 2020, 2 [Member] Interest Rate Swap Expiring November 2020, 2 [Member] Interest Rate Swaps/Caps Interest Rate Swap [Member] Financial Instruments: Derivatives and Hedging Derivative [Line Items] Notional Value Derivative Asset, Notional Amount Strike Rate Derivative, Fixed Interest Rate Fair Value Derivative, Fair Value, Net Gain (loss) from changes in fair value Accumulated Other Comprehensive Income (Loss), Gain (Loss) from Changes in Fair Value Accumulated Other Comprehensive Income (Loss), Gain (Loss) from Changes in Fair Value Fair value of derivatives in a net liability position Derivative, Net Liability Position, Aggregate Fair Value Aggregate termination value Assets Needed for Immediate Settlement, Aggregate Fair Value Estimated current balance held in accumulated other comprehensive loss to be reclassified into earnings within the next 12 months Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months Share of joint venture of accumulated other comprehensive loss reclassified into equity in net income from unconsolidated joint ventures within the next 12 months Cash Flow Hedge Gain (Loss) to be Reclassified within Twelve Months into Equity in Net Income Represents the estimated net amount of existing gains (losses) on cash flow hedges at the reporting date expected to be reclassified to equity in net income within the next 12 months. Amount of Gain (Loss) Recognized in Other Comprehensive Loss (Effective Portion) Unrealized Gain (Loss) on Interest Rate Cash Flow Hedges, Pretax, Accumulated Other Comprehensive Income (Loss) Amount of Loss Reclassified from Accumulated Other Comprehensive Loss into Income (Effective Portion) Interest Rate Cash Flow Hedge Gain (Loss) Reclassified to Earnings, Net Amount of (Loss) Recognized into Income (Ineffective Portion) Gain (Loss) on Interest Rate Cash Flow Hedge Ineffectiveness Initial term of non cancellable operating leases, minimum (in years) Operating Leases, Minimum Lease Term Represents the initial minimum term of the non cancellable operating leases. Capital lease Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments, Fiscal Year Maturity [Abstract] Remaining 2018 Capital Leases, Future Minimum Payments, Remainder of Fiscal Year 2019 Capital Leases, Future Minimum Payments Due, Next Twelve Months 2020 Capital Leases, Future Minimum Payments Due in Two Years 2021 Capital Leases, Future Minimum Payments Due in Three Years 2022 Capital Leases, Future Minimum Payments Due in Four Years 2023 Capital Leases, Future Minimum Payments Due in Five Years Thereafter Capital Leases, Future Minimum Payments Due Thereafter Total minimum lease payments Capital Leases, Future Minimum Payments Due Amount representing interest Capital Leases, Future Minimum Payments, Interest Included in Payments Capital lease obligations Capital Leases, Future Minimum Payments, Present Value of Net Minimum Payments Non-cancellable operating leases Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract] Remaining 2018 Operating Leases, Future Minimum Payments, Remainder of Fiscal Year 2019 Operating Leases, Future Minimum Payments Due, Next Twelve Months 2020 Operating Leases, Future Minimum Payments, Due in Two Years 2021 Operating Leases, Future Minimum Payments, Due in Three Years 2022 Operating Leases, Future Minimum Payments, Due in Four Years 2023 Operating Leases, Future Minimum Payments, Due in Five Years Thereafter Operating Leases, Future Minimum Payments, Due Thereafter Total minimum lease payments Operating Leases, Future Minimum Payments Due Statement of Comprehensive Income [Abstract] Net income Other comprehensive income (loss): Other Comprehensive Income (Loss), Net of Tax [Abstract] Change in net unrealized gain on derivative instruments, including SL Green's/SLGOP's share of joint venture net unrealized (loss) gain on derivative instruments Other Comprehensive Income (Loss), Unrealized Gain (Loss) on Derivatives Arising During Period, Net of Tax Change in unrealized gain on marketable securities Other Comprehensive Income (Loss), Unrealized Holding Gain (Loss) on Securities Arising During Period, Net of Tax Other comprehensive income (loss) Other Comprehensive Income (Loss), Net of Tax Comprehensive income (loss) Comprehensive Income (Loss), Net of Tax, Including Portion Attributable to Noncontrolling Interest Net (income) loss attributable to noncontrolling interests and preferred units distributions Net Income (Loss) Attributable to Noncontrolling Interest Net (loss) income attributable to noncontrolling interests Other comprehensive (loss) income attributable to noncontrolling interests Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Noncontrolling Interest Comprehensive income attributable to SL Green/SLGOP Comprehensive Income (Loss), Net of Tax, Attributable to Parent Net income attributable to SLGOP common unitholders Stock-based compensation plans (shares) Incremental Common Units Attributable to Share based Payment Arrangements Incremental Common Units Attributable to Share based Payment Arrangements Diluted weighted average common units outstanding (shares) Weighted Average Number of Units Outstanding Diluted Weighted Average Number of Units Outstanding Diluted Schedule of Ownership Interests [Table] Schedule of Ownership Interests [Table] Represents information related to ownership interests held by the entity. Series G Preferred Units Series G Preferred Stock [Member] Series F Preferred Units Series F Preferred Stock [Member] Series K Preferred Units Series K Preferred Stock [Member] Series K Preferred Stock [Member] Series L Preferred Units Series L Preferred Stock [Member] Series L Preferred Stock [Member] Series M Preferred Units Series M Preferred Stock [Member] Series M Preferred Stock [Member] Series N Preferred Units Series N Preferred Stock [Member] Series N Preferred Stock [Member] Series O Preferred Units Series O Preferred Stock [Member] Series O Preferred Stock [Member] Series P Preferred Units Series P Preferred Stock [Member] Series P Preferred Stock [Member] Series Q Preferred Units Series Q Preferred Stock [Member] Series Q Preferred Stock [Member] Series R Preferred Units Series R Preferred Stock [Member] Series R Preferred Stock [Member] Series S Preferred Units Series S Preferred Stock [Member] Series S Preferred Stock [Member] Series T Preferred Units Series T Preferred Units [Member] Series T Preferred Units [Member] Series U Preferred Units Series U Preferred Units [Member] Series U Preferred Units [Member] Series A Preferred Units Series A Preferred Stock [Member] Series B Preferred Units Series B Preferred Stock [Member] Organization Ownership Interests [Line Items] -- None. No documentation exists for this element. -- Noncontrolling interest in the operating partnership (as a percent) Noncontrolling Interest, Ownership Percentage by Noncontrolling Owners Number of units of operating partnership owned by the noncontrolling interest unit holders (shares) Minority Interest Units of Partnership Owned by Noncontrolling Owners Represents the number of partnership units owned by the noncontrolling unit holders. Shares of common stock reserved for issuance upon redemption of units of limited partnership interest in operating partnership (shares) Common Stock Capital Shares Reserved Issuance upon Redemption of Units of Limited Partnership Represents the number of common shares reserved for issuance upon redemption of units of the limited partnership interest. Rollforward analysis of the activity relating to the noncontrolling interests in the operating partnership Stockholders' Equity Attributable to Noncontrolling Interest [Roll Forward] Balance at beginning of period Distributions Noncontrolling Interest, Decrease from Distributions to Other Noncontrolling Interest Holders Noncontrolling Interest, Decrease from Distributions to Other Noncontrolling Interest Holders Issuance of common units Redemption of common units Net income Accumulated other comprehensive income allocation Fair value adjustment Minority Interest Increase (Decrease) from Fair Value Adjustment Represents the increase (decrease) in noncontrolling interest resulting from fair value adjustments. Balance at end of period Number of preferred units issued (in shares) Temporary Equity, Shares Issued Liquidation preference of preferred units (in dollars per share) Temporary Equity, Liquidation Preference Per Share Annual dividends on preferred units (in dollars per share) Preferred Stock, Dividends, Per Share, Cash Paid Operating partnership common stock value use for conversion of preferred units (in dollars per share) Operating Partnership Common Unit Value, Per Share Use for Conversion Represents the common stock value per share which is used for purposes of determining the number of operating partnership common stock issue on conversion of preferred unit. Number of company common stock issue on redemption of operation partnership common units Operating Partnership Common Unit, Convertible Conversion Ratio Operating Partnership Common Unit, Convertible Conversion Ratio Mandatory liquidation preference (in dollars per share) Temporary Equity, Liquidation Preference Preferred units, shares authorized (in shares) Preferred Units, Authorized Number of company common stock issued on conversion of Series B preferred units Preferred Stock, Convertible Conversion Ratio Preferred Stock, Convertible Conversion Ratio Senior unsecured notes Senior Unsecured Notes [Member] Senior Unsecured Notes [Member] Senior Unsecured Bonds Senior Unsecured Bonds [Member] Senior Unsecured Bonds 5.00% Senior unsecured notes maturing on August 15, 2018 Senior Unsecured Notes, Due August 15, 2018 [Member] Represents senior unsecured notes bearing an interest rate of 5 percent maturing on August 15, 2018. 7.75% Senior unsecured notes maturing on March 15, 2020 Senior Unsecured Notes Due March 15, 2020 [Member] Represents senior unsecured notes maturing on March 15, 2020. 4.50% Senior unsecured notes maturing on December 1, 2022 Senior Unsecured Notes Due December 1, 2022 [Member] Represents senior unsecured notes bearing an interest rate of 4.50 percent maturing on December 1, 2022. 4.27% Senior unsecured notes maturing on December 17, 2025 Senior Unsecured Note Due December 17, 2025 [Member] Senior Unsecured Note Due December 17, 2025 [Member] 4.50% Senior Unsecured Bonds Due December 2022 4.50 Percent Senior Unsecured Bonds Due December 2022 [Member] 4.50 Percent Senior Unsecured Bonds Due December 2022 [Member] 3.25 Percent Senior Unsecured Notes Due October 2022 3.25 Percent Senior Unsecured Notes Due October 2022 [Member] 3.25 Percent Senior Unsecured Notes Due October 2022 Debt Instrument [Line Items] Debt disclosures by scheduled maturity date Debt Instrument, Information by Scheduled Maturity Date of Debt [Abstract] -- None. No documentation exists for this element. -- Unpaid Principal Balance Long-term Debt, Gross Accreted Balance Accreted Balance, net of deferred financing costs Senior Notes, Net of Deferred Finance Costs Senior Notes, Net of Deferred Finance Costs Coupon Rate (as a percent) Debt Instrument, Interest Rate, Stated Percentage Initial Term (in Years) Redemption price, percentage Debt Instrument, Redemption Price, Percentage Loan reserves Provision for Loan and Lease Losses Fair Value Measurements, Recurring and Nonrecurring [Table] Fair Value Measurements, Recurring and Nonrecurring [Table] Investment, Name [Axis] Investment, Name [Axis] Investment, Name [Domain] Investment, Name [Domain] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Axis] Major Types of Debt and Equity Securities [Domain] Major Types of Debt and Equity Securities [Domain] Equity marketable securities Equity Securities [Member] Commercial mortgage-backed securities Commercial Mortgage Backed Securities [Member] Fair Value, Hierarchy [Axis] Fair Value, Hierarchy [Axis] Fair Value, Measurements, Fair Value Hierarchy [Domain] Fair Value Hierarchy [Domain] Level 1 Fair Value, Inputs, Level 1 [Member] Level 2 Fair Value, Inputs, Level 2 [Member] Level 3 Fair Value, Inputs, Level 3 [Member] Measurement Basis [Axis] Measurement Basis [Axis] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Portion at Fair Value Measurement [Member] Portion at Fair Value Measurement [Member] Carrying Value Reported Value Measurement [Member] Fair Value Estimate of Fair Value Measurement [Member] Balance Sheet Location [Axis] Balance Sheet Location [Axis] Balance Sheet Location [Domain] Balance Sheet Location [Domain] Fair Value of Financial Instruments Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Marketable securities Available-for-sale Securities Interest rate cap and swap agreements (included in other assets) Derivative Asset, Fair Value, Gross Asset Notes receivable Mortgage Loans on Real Estate, Face Amount of Mortgages Accrued interest Debt and preferred equity investments Fixed rate debt Long-term Debt, Percentage Bearing Fixed Interest, Amount Variable rate debt Long-term Debt, Percentage Bearing Variable Interest, Amount Total Long-term Debt, Fair Value Equity method investments Additional amount of financing receivables included in other assets Financing Receivable, Recorded in Other Assets Represents the amount of financing receivables recorded in other assets on the entity's balance sheet. Estimated fair value of debt and preferred equity investments, low end of range Mortgage Loans on Real Estate, Fair Value, Low End of Range Represents the low end of the range of estimated fair value for investments in mortgage loans on real estate. Estimated fair value of debt and preferred equity investments, high end of range Mortgage Loans on Real Estate Fair Value, High End of Range Represents the high end of the range of estimated fair value for investments in mortgage loans on real estate. Related Party Transactions [Abstract] Related Party Transactions Related Party Transactions Disclosure [Text Block] Income taxes Income Tax Disclosure [Abstract] Federal, state and local tax provision Income Tax Expense (Benefit) Schedule of Segment Reporting Information, by Segment [Table] Schedule of Segment Reporting Information, by Segment [Table] Consolidation Items [Axis] Consolidation Items [Axis] Consolidation Items [Domain] Consolidation Items [Domain] Operating Segments Operating Segments [Member] Business Segments [Axis] Segments [Axis] Segment [Domain] Segments [Domain] Real Estate Segment Real Estate Segment [Member] Represents the information pertaining to the reportable segment of the entity, Real Estate Segment. Debt and Preferred Equity Segment Structured Finance Segment [Member] Represents the information pertaining to the reportable segment of the entity, Structured Finance Segment. Segment information Segment Reporting Information [Line Items] Number of reportable segments (segment) Number of Reportable Segments Total revenues Net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities Income (Loss) from Continuing Operations before Realized Gain (Loss) on Disposal of Equity Method Investment This element represents the income or loss from continuing operations attributable to the economic entity which may also be defined as revenue less expenses and taxes from ongoing operations before realized gains (losses) on disposals of equity method investments, extraordinary items, and noncontrolling interest. Total assets Schedule of calculation of numerator and denominator in earnings per unit Schedule of Calculation of Numerator and Denominator in Earnings Per Unit [Table Text Block] Schedule of Calculation of Numerator and Denominator in Earnings Per Unit [Table Text Block] Statement of Stockholders' Equity [Abstract] Cash distribution declared, per common share (in dollars per share) One Madison Avenue One Madison Avenue [Member] Represents information pertaining to One Madison Avenue, a property owned by the entity. 762 Madison Avenue Madison Avenue 762 [Member] Represents information pertaining to property located at 762 Madison Avenue, owned by the entity. 100 Church Street Church Street, 100 [Member] Represents the information pertaining to 100 Church Street, a property owned by the entity. 400 East 58th Street East 400 Street 58 [Member] Represents information pertaining to 400 East 58th Street, a property owned by the entity. Landmark Square Landmark Square [Member] Represents the information pertaining to Landmark Square, a property owned by the entity. 485 Lexington Avenue Lexington Avenue, 485 [Member] Represents the information pertaining to 485 Lexington Avenue, a property owned by the entity. 1080 Amsterdam Avenue Amsterdam Avenue 1080 [Member] Represents information pertaining to property located at 1080 Amsterdam, owned by the entity. 315 West 33rd Street 315 West 33rd Street [Member] 315 West 33rd Street [Member] 719 Seventh Avenue Seven One Nine Seventh Avenue [Member] Seven One Nine Seventh Avenue [Member] 183, 187 Broadway & 5-7 Dey Street 187 Broadway and 5-7 Dey Street [Member] 187 Broadway and 5-7 Dey Street [Member] 220 East 42nd Street East 220 Street 42 [Member] Represents the information pertaining to 220 East 42nd Street, a property owned by the entity. Unsecured Loan Unsecured Debt [Member] Subordinate loan Senior Subordinated Loans [Member] Uncommitted Master Repurchase Agreements Uncommitted Master Repurchase Agreements [Member] Uncommitted Master Repurchase Agreements [Member] Uncommitted Master Repurchase Agreement 2017 Uncommitted Master Repurchase Agreement 2017 [Member] Uncommitted Master Repurchase Agreement 2017 Uncommitted Master Repurchase Agreement 2016 Uncommitted Master Repurchase Agreement 2016 [Member] Uncommitted Master Repurchase Agreement 2016 [Member] Series J Preferred Units Series J Preferred Stock [Member] Series J Preferred Stock [Member] Weighted Average Weighted Average [Member] Mortgages reclassed to liabilities related to assets held for sale Secured Debt, Amount Transferred to Liabilities Related to Net Assets Held for Sale Secured Debt, Amount Transferred to Liabilities Related to Net Assets Held for Sale Total mortgages and other loans payable Secured Debt, Gross Secured Debt, Gross Deferred financing costs, net of amortization Secured Debt, Deferred Finance Costs, Net Secured Debt, Deferred Finance Costs, Net Total mortgages and other loans payable, net Total fixed rate debt Secured Debt, Bearing Fixed Interest, Mortgage Amount Secured Debt, Bearing Fixed Interest, Mortgage Amount Subordinate loan Secured Debt, Bearing Fixed Interest, Subordinate Loan Amount Secured Debt, Bearing Fixed Interest, Subordinate Loan Amount Limited partnership interest Redeemable Noncontrolling Interest, Equity, Carrying Amount Preferred units (as a percent) Preferred units, liquidation preference (in dollars per unit) Book value of collateral Collateral Already Posted, Aggregate Fair Value Number of debt instruments Debt Instrument, Number of Instruments Debt Instrument, Number of Instruments Basis point fee (as a percent) Line of Credit Facility, Basis Point Fee Line of Credit Facility, Basis Point Fee Threshold amount for basis point fee to be applicable (less than) Line of Credit Facility, Threshold Amount for Basis Point Fee Line of Credit Facility, Threshold Amount for Basis Point Fee Deferred Costs Deferred Financing and Leasing Costs Disclosure [Text Block] Costs incurred in connection with financing activities (fees to banks) and costs incurred in connection with leasing activities (fees to real estate brokers), net of amortization. Reconciliation of income from continuing operations to net income attributable to SL Green common stockholders Net income before equity in net (loss) gain on sale of interest in unconsolidated joint venture/real estate, purchase price and other fair value adjustments, gain on sale of real estate, net, depreciable real estate reserves, and gain on sale of investment in marketable securities Organization and Basis of Presentation Organization, Consolidation and Presentation of Financial Statements Disclosure [Text Block] Organization Percentage of ownership in SL Green Management LLC owned by operating partnership (percent) Subsidiary of Limited Liability Company or Limited Partnership, Ownership Interest Schedule of Real Estate Properties [Table] Schedule of Real Estate Properties [Table] Manhattan Manhattan [Member] Represents information pertaining to properties located in Manhattan. Suburban Suburban [Member] Represents information pertaining to property located in Suburban areas. Real Estate Property Ownership [Axis] Real Estate Property Ownership [Axis] Real Estate Properties [Domain] Real Estate Properties [Domain] Consolidated properties Consolidated Properties [Member] Unconsolidated properties Unconsolidated Properties [Member] Office Office Properties [Member] Represents the investment in office properties owned by the entity. Retail Retail Properties [Member] Represents information pertaining to retail properties owned by the entity. Development/Redevelopment Development Properties [Member] Represents the development properties owned by the entity. Fee Interest Fee Interest [Member] Fee Interest [Member] Commercial properties Commercial Property [Member] Commercial Property [Member] Residential Residential Real Estate [Member] Dual property type, retail portion Dual Property Type, Retail Portion [Member] Dual Property Type, Retail Portion [Member] Dual property type, residential portion Dual Property Type, Residential Portion [Member] Dual Property Type, Residential Portion [Member] Managed office properties Managed Office Properties [Member] Represents the office properties managed by the entity. Real estate properties Real Estate Properties [Line Items] Number of Properties Number of Real Estate Buildings Number of Real Estate Buildings Approximate Square Feet unaudited (sqft) Weighted Average Occupancy unaudited (as a percent) Real Estate Weighted Average Occupancy Represents the weighted average occupancy of real estate properties owned, which represents the total leased square feet divided by the total available rentable square feet. Debt and preferred equity investments including investments held by unconsolidated joint ventures Mortgage Loans on Real Estate, Commercial and Consumer, Net Including Debt Investments, Other Mortgage Loans on Real Estate, Commercial and Consumer, Net Including Debt Investments, Other Debt and preferred equity investments and other financing receivables included in other balance sheet items Debt Investments, Other Debt Investments, Other Number of shares to be received on redemption of one unit of limited partnership interests (shares) Number of Shares on Redemption of One Unit of Partnership Interest Represents the number of shares of the common stock of the entity, which the limited partner of the operating partnership is entitled to receive on redemption of one unit of interest in the partnership. Variable Interest Entities [Axis] Variable Interest Entities [Axis] Variable Interest Entity, Classification [Domain] Variable Interest Entity, Classification [Domain] Consolidated VIEs Variable Interest Entity, Primary Beneficiary [Member] Tenant and other receivables, allowance Allowance for Doubtful Accounts, Premiums and Other Receivables Deferred rents receivable, allowance Allowance for Deferred Rents Receivable The valuation allowances attributable to, for instance, credit risk associated with a lessee as of the balance sheet date to reduce the gross amount of deferred rents receivable, which would be presented in parentheses on the face of the balance sheet. Debt and preferred equity investments, discount and deferred origination fees Discount of Structured Finance Investments This item represents the net amount of discounts related to investments in structured finance investments. Preferred stock, liquidation preference (in dollars per share) Preferred stock, shares issued (in shares) Preferred Stock, Shares Issued Limited partner interests in Operating Partnership, limited partner common units outstanding (shares) Limited Partners' Capital Account, Units Outstanding Preferred units, liquidation preference (in dollars per share) Preferred units, shares issued (in shares) Preferred units, shares outstanding (in shares) Temporary Equity, Shares Outstanding Common stock, shares issued (in shares) Common Stock, Shares, Issued Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Treasury stock, shares (in shares) Treasury Stock, Shares SL Green partner's capital, general partner common units outstanding (shares) General Partners' Capital Account, Units Outstanding SL Green partners' capital, limited partner common units outstanding (shares) Limited Partnership Units Held by General Partner This element represents Limited Partnership Units Held by General Partner. Accumulated depreciation Statement of Partners' Capital [Abstract] Stonehenge Portfolio Stonehenge Portfolio [Member] Stonehenge Portfolio [Member] Mezzanine loan due July 2036 Mezzanine Loan Due July 2036 [Member] Mezzanine Loan Due July 2036 [Member] Mezzanine loan due February 2022 Participating Financing Due February 2022 [Member] Participating Financing Due February 2022 [Member] Mezzanine Loan and Preferred Equity, Due March 2018 Mezzanine Loan And Preferred Equity, Due March 2018 [Member] Mezzanine Loan And Preferred Equity, Due March 2018 [Member] Mezzanine Loans And Preferred Equity [Member] Mezzanine Loans And Preferred Equity [Member] Mezzanine Loans And Preferred Equity [Member] Schedule of Equity Method Investments [Line Items] Gross Asset Valuation Disposal Group, Including Discontinued Operation, Consideration Class of Treasury Stock Class of Treasury Stock [Table Text Block] Schedule of Earnings Per Share Schedule of Earnings Per Share, Basic and Diluted [Table Text Block] Disposal Group Classification [Axis] Disposal Group Classification [Axis] Disposal Group Classification [Domain] Disposal Group Classification [Domain] Discontinued Operations, Disposed of by Sale [Member] Discontinued Operations, Disposed of by Sale [Member] Schedule of general information on joint ventures Equity Method Investments [Table Text Block] Schedule of first mortgage notes payable collateralized by the respective joint venture properties and assignment of leases Schedule of Mortgage and Other Loans Payable on Joint Venture Properties [Table Text Block] Tabular disclosure of the information pertaining to mortgage and other loans payable on joint venture properties of the entity. Schedule of combined balance sheets for the unconsolidated joint ventures Equity Method Investments, Summarized Financial Information Balance Sheet [Table Text Block] Disclosure of summarized balance sheet financial information for investments accounted for using the equity method of accounting. Schedule of combined statements of income for the unconsolidated joint ventures Equity Method Investments, Summarized Financial Information Income Statement [Table Text Block] Disclosure of summarized income statement information for investments accounted for using the equity method of accounting. Discontinued Operations and Disposal Groups [Abstract] Disposal Groups, Including Discontinued Operations [Table] Disposal Groups, Including Discontinued Operations [Table] International Drive 1-6 1-6 International Drive [Member] 1-6 International Drive [Member] 115-117 Stevens Avenue Stevens Avenue, 115 to 117 [Member] Represents the information pertaining to 115-117 Stevens Avenue, a property owned by the entity. 600 Lexington Ave 600 Lexington Ave [Member] 600 Lexington Ave [Member] 635 Madison Avenue Madison Avenue 635 [Member] Madison Avenue 635 [Member] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] Properties Sold [Abstract] Properties Sold [Abstract] Properties Sold [Abstract] Approximate Square Feet Sales Price Charge expected to be recorded Disposal Group, Not Discontinued Operation, Loss (Gain) on Write-down Gain on Sale (Loss) Discontinued Operation, Gain (Loss) on Disposal of Discontinued Operation, Net of Tax Schedule of selected results of operations and selected asset information Schedule of Segment Reporting Information, by Segment [Table Text Block] Schedule of reconciliation of income from continuing operations to net income attributable to SL Green common stockholders Schedule of Income (Loss) Available to Common Stockholders [Table Text Block] Tabular disclosure of the information pertaining to income (loss) attributable to common stockholders of the entity. This item may include reconciliation of income (loss) from continuing operations to net income (loss) attributable to common stockholders. Partners' Capital of the Operating Partnership Stockholders' Equity of the Company Schedule of future minimum rental payments for operating leases Schedule of Future Minimum Rental Payments for Operating Leases [Table Text Block] Schedule of future minimum rental payments for capital leases Schedule of Future Minimum Lease Payments for Capital Leases [Table Text Block] Schedule of Related Party Transactions, by Related Party [Table] Schedule of Related Party Transactions, by Related Party [Table] Alliance Building Services Alliance Building Services [Member] Represents the information pertaining to Alliance Building Services, which is a related party of the entity. Entity with Stephen L Green ownership interest Related Party Stephen L Green Interest [Member] Represents the information pertaining to an entity in which Stephen L. Green owns an interest, which is a related party of the entity. Marc Holliday Investor [Member] Andrew Mathias Investor 2 [Member] Investor 2 [Member] Related Party Transactions Related Party Transaction [Line Items] Profit participation from related party Related Party Transaction, Other Revenues from Transactions with Related Party Payments made for services Related Party Transaction, Expenses from Transactions with Related Party Property management fees from related party Revenue from Related Parties Percentage of profits due to investors (as a percentage) Related Party Transaction, Percentage of Profits Due to Investors Related Party Transaction, Percentage of Profits Due to Investors Due from related party Related Party Transaction, Due from (to) Related Party Amounts due from/to related parties Due from Related Parties, Unclassified [Abstract] Due from joint ventures Due from Joint Ventures Other Due from Other Related Parties Related party receivables Accounting Standards Update 2014-09 Accounting Standards Update 2014-09 [Member] Preferred Stock Additional Paid-In-Capital Additional Paid-in Capital [Member] Treasury Stock Treasury Stock [Member] Retained Earnings Retained Earnings [Member] Noncontrolling Interests Noncontrolling Interest [Member] Increase (Decrease) in Stockholders' Equity Increase (Decrease) in Stockholders' Equity [Roll Forward] Beginning Balance (in shares) Cumulative adjustment upon adoption of ASC 610-20 Cumulative Effect of New Accounting Principle in Period of Adoption Adjusted Balance Stockholders' Equity, Including Portion Attributable to Noncontrolling Interest, Adjusted Balance Net income Profit (Loss) Less Minority Interest in Net Income (Loss) Operating Partnerships Net income including minority interest in partnerships. Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Portion Attributable to Parent Preferred dividends DRSPP proceeds (in shares) Stock Issued During Period, Shares, Dividend Reinvestment Plan DRSPP proceeds Stock Issued During Period, Value, Dividend Reinvestment Plan Reallocation of noncontrolling interest in the Operating Partnership Reallocation of Noncontrolling Interest to (from) Operating Partnership Reallocation of Noncontrolling Interest to (from) Operating Partnership Deferred compensation plan and stock awards, net (in shares) Deferred Compensation Plan and Stock Award, Shares Number of shares issued during the period from a Deferred Compensation Plan and Stock Award. Deferred compensation plan and stock awards, net of forfeitures and tax withholdings Deferred Compensation Plan and Stock Award, Net Value of stock issued during the period from a deferred compensation plan and stock award, net. Repurchases of common stock (in shares) Repurchases of common stock Treasury Stock, Value, Acquired, Cost Method Proceeds from stock options exercised (in shares) Common Stock Issued During Period, Shares New Issues This element represents the number of new common stock issued during the period. Proceeds from stock options exercised Common Stock Issued During Period, Value New Issues This element represents the value of new common stock issued during the period. Contributions to consolidated joint venture interests Consolidation of Joint Venture Interest This element represent the net income (loss) in consolidation of joint venture interest. Deconsolidation of partially owned entity Noncontrolling Interest, Decrease from Deconsolidation Cash distributions to noncontrolling interests Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders Cash distributions declared ($0.8125 per common share, none of which represented a return of capital for federal income tax purposes) Dividends, Common Stock Ending Balance (in shares) Mortgages and other loans payable Summary of properties sold Disposal Groups, Including Discontinued Operations [Table Text Block] Series I Preferred Units Units outstanding (units) Period of restriction to redeem OP Units Common Units Redemption, Period Of Restriction Common Units Redemption, Period Of Restriction Conversion of stock, shares issued Conversion of Stock, Shares Issued Noncontrolling interest in the operating partnership (as a percent) Number of units of operating partnership owned by the noncontrolling interest unit holders (units) Junior Mortgage Participation Acquired in September 2014 Junior Mortgage Participation Acquired in September 2014 [Member] Junior Mortgage Participation Acquired in September 2014 [Member] Receivable with Imputed Interest, Face Amount Payments to acquire loans Payments to Acquire Loans Receivable Number of portfolio segments of financial receivables (segment) Financing Receivable, Portfolio Segments Number Represents the number of portfolio segments of financing receivables. Trust Preferred Securities Junior Subordinated Debt [Member] Mortgages and other loans payable Mortgage and Other Loans Payable [Member] Represents mortgage and other loans payable of the entity. Revolving Credit Facility Unsecured Term Loans Senior Unsecured Notes Senior Notes [Member] Proceeds from issuance of debt Proceeds from Issuance of Debt Scheduled Amortization Future Amortization of Debt [Abstract] -- None. No documentation exists for this element. -- Remaining 2018 Future Amortization of Debt, First Full Fiscal Year The amount of amortization of debt expected to be recognized during the first full fiscal year following the date of the most recent balance sheet. 2019 Future Amortization of Debt, Second Full Fiscal Year The amount of amortization of debt expected to be recognized during the second full fiscal year following the date of the most recent balance sheet. 2020 Future Amortization of Debt, Third Full Fiscal Year The amount of amortization of debt expected to be recognized during the third full fiscal year following the date of the most recent balance sheet. 2021 Future Amortization of Debt Fourth Full Fiscal Year The amount of amortization of debt expected to be recognized during the fourth full fiscal year following the date of the most recent balance sheet. 2022 Future Amortization of Debt Fifth Full Fiscal Year The amount of amortization of debt expected to be recognized during the fifth full fiscal year following the date of the most recent balance sheet. Thereafter Future Amortization of Debt after Fifth Full Fiscal Year The amount of amortization of debt expected to be recognized after the fifth full fiscal year following the date of the most recent balance sheet. Total amortization of debt Future Amortization of Debt The total expected future amortization of debt. Principal Repayments and Joint Venture Debt Maturities of Long-term Debt [Abstract] Remaining 2018 Long-term Debt, Maturities, Repayments of Principal in Next Twelve Months 2019 Long-term Debt, Maturities, Repayments of Principal in Year Two 2020 Long-term Debt, Maturities, Repayments of Principal in Year Three 2021 Long-term Debt, Maturities, Repayments of Principal in Year Four 2022 Long-term Debt, Maturities, Repayments of Principal in Year Five Thereafter Long-term Debt, Maturities, Repayments of Principal after Year Five Total principal repayments Long Term Debt, Maturities, Repayments of Principal Total amount of long-term debt maturing in future periods. Schedule of amounts due from/to related parties Schedule of Related Party Transactions [Table Text Block] Deferred leasing costs Deferred Costs, Leasing, Gross Less: accumulated amortization Accumulated Amortization of Deferred Costs The accumulated amortization, as of the reporting date, representing the periodic charge to earnings of deferred costs. Deferred costs, net Document and Entity Information -- None. No documentation exists for this element. -- Document Information [Table] Document Information [Table] Document Information [Line Items] Document Information [Line Items] Entity Registrant Name Entity Registrant Name Entity Central Index Key Entity Central Index Key Current Fiscal Year End Date Current Fiscal Year End Date Entity Filer Category Entity Filer Category Document Type Document Type Document Period End Date Document Period End Date Document Fiscal Year Focus Document Fiscal Year Focus Document Fiscal Period Focus (Q1,Q2,Q3,FY) Document Fiscal Period Focus Amendment Flag Amendment Flag Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Statement of Cash Flows [Abstract] Operating Activities Net Cash Provided by (Used in) Operating Activities [Abstract] Adjustments to reconcile net income to net cash provided by operating activities: Adjustments, Noncash Items, to Reconcile Net Income (Loss) to Cash Provided by (Used in) Operating Activities [Abstract] Depreciation and amortization Depreciation, Depletion and Amortization Equity in net income from unconsolidated joint ventures Distributions of cumulative earnings from unconsolidated joint ventures Proceeds from Equity Method Investment, Distribution Equity in net loss (gain) on sale of interest in unconsolidated joint venture interest/real estate Purchase price and other fair value adjustments Purchase Price, Fair Value Adjustment Purchase Price, Fair Value Adjustment Depreciable real estate reserves Depreciable Real Estate Reserves, Cash Flow Effect Depreciable Real Estate Reserves, Cash Flow Effect Gain on sale of real estate, net Gain on sale of investments in marketable securities Marketable Securities, Gain (Loss), Cash Flow Effect Marketable Securities, Gain (Loss), Cash Flow Effect Deferred rents receivable Straight Line Rent Other non-cash adjustments Other Noncash Income (Expense) Changes in operating assets and liabilities: Increase (Decrease) in Operating Capital [Abstract] Tenant and other receivables Increase (Decrease) in Accounts Receivable Related party receivables Increase (Decrease) in Due from Related Parties, Current Deferred lease costs Increase (Decrease) in Deferred Leasing Fees Other assets Increase (Decrease) in Other Operating Assets Accounts payable, accrued expenses, other liabilities and security deposits Increase (Decrease) in Accrued Liabilities and Other The change during the period in carrying value of accounts payable, accrued expenses and fair value of hedges, due within one year or operating cycle. Deferred revenue and land leases payable Increase (Decrease) in Deferred Liabilities Net cash provided by operating activities Net Cash Provided by (Used in) Operating Activities Investing Activities Net Cash Provided by (Used in) Investing Activities [Abstract] Acquisitions of real estate property Payments to Acquire Real Estate Additions to land, buildings and improvements Payments to Acquire Productive Assets Acquisition deposits and deferred purchase price Increase (Decrease) in Restricted Cash Investments in unconsolidated joint ventures Payments to Acquire Equity Method Investments Distributions in excess of cumulative earnings from unconsolidated joint ventures Proceeds from Equity Method Investment Dividends or Distributions This item represents to disclosure of the amount of dividends or other distributions received from unconsolidated subsidiaries, certain corporate joint ventures, and certain noncontrolled corporation. Distributions constitute a return of investment. Net proceeds from disposition of real estate/joint venture interest Proceeds from Real Estate and Real Estate Joint Ventures Proceeds from sale or redemption of marketable securities Proceeds from Sale and Maturity of Marketable Securities Other investments Payments for (Proceeds from) Investments Origination of debt and preferred equity investments Payments to Acquire Investments Repayments or redemption of debt and preferred equity investments Proceeds from Sale and Maturity of Other Investments Net cash provided by investing activities Net Cash Provided by (Used in) Investing Activities Financing Activities Net Cash Provided by (Used in) Financing Activities [Abstract] Proceeds from mortgages and other loans payable Proceeds from Issuance of Secured Debt Repayments of mortgages and other loans payable Repayments of Secured Debt Proceeds from revolving credit facility and senior unsecured notes Proceeds from Other Debt Repayments of revolving credit facility and senior unsecured notes Repayments of Other Debt Proceeds from stock options exercised and DRIP issuance Proceeds from Stock Options Exercised Repurchase of common stock Payments for Repurchase of Common Stock Redemption of preferred stock Payments for Repurchase of Redeemable Preferred Stock Distributions to noncontrolling interests in other partnerships Distributions to Noncontrolling Interests Other Partnerships The cash outflow for distributions to the entity's partner from a consolidated joint venture. Contributions from noncontrolling interests in other partnerships Proceeds from Noncontrolling Interests in Other Partnerships The cash inflow from the capital received in cash from a partner in a consolidated partnership during the period. Distributions to noncontrolling interests in the Operating Partnership Distribution to Noncontrolling Interest Operating Partnership The cash outflow for distributions to partners in a partnership. Dividends / Distributions paid on common and preferred stock / units Payments of Dividends Tax withholdings related to restricted share awards Payments Related to Tax Withholding for Share-based Compensation Deferred loan costs and capitalized lease obligation Deferred Loan Costs and Capitalized Lease Obligation The net change during the reporting period in the finance costs incurred in connection with a loan. The capitalized lease obligation is a straight-line adjustment for ground lease obligations. Net cash (used in) provided by financing activities Net Cash Provided by (Used in) Financing Activities Net increase in cash, cash equivalents, and restricted cash Cash, Cash Equivalents, Restricted Cash and Restricted Cash Equivalents, Period Increase (Decrease), Including Exchange Rate Effect Cash, cash equivalents, and restricted cash at beginning of year Cash, cash equivalents, and restricted cash at end of period Supplemental Disclosure of Non-Cash Investing and Financing Activities: Cash Flow, Noncash Investing and Financing Activities Disclosure [Abstract] Issuance of units in the Operating Partnership Partners' Capital Account, Sale of Units Redemption of units in the Operating Partnership for stock Partners' Capital Account, Redemptions Derivative instruments at fair value Derivative Instruments Fair Value Adjustment Represents fair value adjustments to derivative instruments. Tenant improvements and capital expenditures payable Capital Expenditures Incurred but Not yet Paid Fair value adjustment to noncontrolling interest in Operating Partnership Operating Partnership Noncontrolling Interest Fair Value Adjustment Represents the fair value adjustment to the noncontrolling interest in the operating partnership. Deconsolidation of subsidiaries Deconsolidation Real Estate Investments Represents the change in the carrying value of real estate investments resulting from deconsolidation. Transfer of assets related to assets held for sale Transfer to Net Assets Held For Sale Value of assets transferred to assets held-for-sale in noncash transactions during the reporting period. Transfer of liabilities related to assets held for sale Transfer to Liabilities Related to Net Assets Held For Sale Value of liabilities transferred to liabilities related to assets held-for-sale in noncash transactions during the reporting period. Deferred leasing payable Deferred Lease Payable Deferred Lease Payable Removal of fully depreciated commercial real estate properties Removal of Fully Depreciated Real Estate Assets Removal of Fully Depreciated Real Estate Assets Share repurchase payable Share Repurchases Payable Share Repurchases Payable Total cash, cash equivalents, and restricted cash Schedule of Noncontrolling Interest Schedule of Noncontrolling Interest [Table Text Block] Tabular disclosure of the information pertaining to the noncontrolling interest. Schedule of Preferred Unit Activity Schedule of Preferred Units [Table Text Block] Partner Capital Components [Axis] Partner Capital Components [Axis] Partner Capital Components [Domain] Partner Capital Components [Domain] Partners' Interest General Partner [Member] Increase (Decrease) in Partner's Capital Beginning Balance Beginning Balance (units) Partners' Capital Account, Units Adjusted Balance Partners' Capital, Adjusted Balance Net income Profit Loss, Less Preferred Distributions The consolidated profit or loss for the period, net of income taxes, including the portion attributable to the noncontrolling interest, less preferred distributions during the period. Other comprehensive income Other Comprehensive Income (Loss), Net of Tax, Less Portion Attributable to Noncontrolling Interest Other Comprehensive Income (Loss), Net of Tax, Less Portion Attributable to Noncontrolling Interest Preferred distributions Distributions Preferred Units Distributions declared for preferred units during the period. DRSPP proceeds Reallocation of noncontrolling interests in the operating partnership Deferred compensation plan and stock awards, net of forfeitures and tax withholdings Contribution to consolidated joint venture interests Contributions - proceeds from stock options exercised (in shares) Contributions - proceeds from stock options exercised Partners' Capital Account, Option Exercise Cash distributions declared ($0.8125 per common unit, none of which represented a return of capital for federal income tax purposes) Partners' Capital Account, Distributions Ending Balance Ending Balance (units) Properties Held for Sale and Property Dispositions Disposal Groups, Including Discontinued Operations, Disclosure [Text Block] Investment in Marketable Securities Cost basis Available-for-sale Securities, Amortized Cost Basis Proceeds from sale of marketable securities Proceeds from Sale of Available-for-sale Securities Marketable Securities, Realized Gain (Loss) Marketable Securities, Realized Gain (Loss)