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Data Type:	num:percentItemType
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Represents the duration of each offering period during which the shares are offered for purchase under the stock-based compensation plan of the entity.

No definition available.

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Period Type:	instant

Represents the approximate amount of awards that may be earned by the recipients of the stock-based compensation plan of the entity depending upon the appreciation of the price of stock of the entity above a threshold level.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsApproximateAmountOfAwardsThatMayBeEarned
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Represents the approximate amount of awards that may be earned by the recipients of the plan any time after the beginning of the second year, if the maximum performance has been achieved.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsApproximateAmountOfAwardsThatMayBeEarnedAnyTimeAfterStartOfSecondYear
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Represents the approximate amount of awards that may be earned by the recipients of the plan any time after the beginning of the third year, if the maximum performance has been achieved.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsApproximateAmountOfAwardsThatMayBeEarnedAnyTimeAfterStartOfThirdYear
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Period Type:	instant

Represents the awards earned by all participants under the stock based compensation plans.

No definition available.

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Represents the consecutive number of days over which maximum performance must be maintained in order to earn the award earlier than the standard period.

No definition available.

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Represents the aggregate fair value of awards on the date of grant.

No definition available.

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Represents the percentage of equity-based awards other than stock (or unit) options granted as of the balance sheet date.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsPercentage
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Represents the amount of the maximum dilution cap on the value of awards that could be earned under stock based compensation plans.

No definition available.

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Data Type:	xbrli:monetaryItemType
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Period Type:	instant

Represents the maximum dilution cap on the awards that could be earned under stock based compensation plans expressed as a percentage of the entity's outstanding shares and units of limited partnership interest.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsMaximumDilutionCapAsPercentageOfOutstandingSharesAndUnitsOfLimitedPartnership
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Balance Type:	na
Period Type:	instant

Under the compensation program, represents the maximum performance pool, net of forfeitures, established based on the successful attainment of performance hurdles.

No definition available.

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Represents the maximum number of potential award units to be granted under the stock-based compensation plan of the entity.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsMaximumPotentialAwards
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Represents the percentage of aggregate stock price appreciation below which no awards will be earned by recipients of the stock-based compensation plan of the entity.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsMinimumPercentageOfAggregateStockPriceAppreciationRequiredToEarnAwards
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Data Type:	num:percentItemType
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Period Type:	instant

Represents the minimum percentage of stock price appreciation at which the maximum approximate amount of awards will be earned by recipients of the stock-based compensation plan.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsMinimumPercentageStockPriceAppreciationToEarnMaximumAmount
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the percentage of value of the award amortized over the period of five years from the date of grant.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfAggregateValueAmortizedOverFiveYears
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Data Type:	num:percentItemType
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Period Type:	duration

Represents the percentage of value of the award amortized over the period of six years from the date of grant.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfAggregateValueAmortizedOverSixYears
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of awards earned which will be vesting on January 1, 2013.

No definition available.

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Period Type:	instant

Represents the percentage of awards earned which will be vesting on January 1, 2014.

No definition available.

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the percentage of awards earned which will be vesting on January 1, 2015.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfAwardsVestingOnJanuary12015
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the percentage of each award which vested upon attainment date of performance hurdles.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfEachAwardVested
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the percentage of value of the award amortized over the period of four years from the date of grant.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfValueAmortizedOverFourYears
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of value of the award amortized over the period of seven years from the date of grant.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfValueAmortizedOverSevenYears
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Data Type:	num:percentItemType
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Period Type:	duration

Of the percentage of value of the award amortized over five years from the date of grant, represents the percentage amortized per year for the five-year period.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfValueAmortizedPerYearForFiveYears
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Data Type:	num:percentItemType
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Period Type:	duration

Of the percentage of value of the award amortized over seven years from the date of grant, represents the percentage amortized per year for the seven-year period.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfValueAmortizedPerYearForSevenYears
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Of the percentage of value of the award amortized over six years from the date of grant, represents the percentage amortized per year for the six-year period.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfValueAmortizedPerYearForSixYears
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

Represents the percentage of stock price appreciation at which the minimum approximate amount of awards will be earned by recipients of the stock-based compensation plan.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageStockPriceAppreciationToEarnMinimumAmount
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the threshold percentage of return to be achieved by the holders of the entity's common equity, above which awards may be granted to plan participants.

No definition available.

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Data Type:	num:percentItemType
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Represents the period over which the return achieved by the holders of the entity's common equity is measured to determine eligibility to grant awards.

No definition available.

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Period Type:	duration

Represents the period for appreciation of the stock price of the entity to be taken into consideration for arriving at the amount of awards to be granted under the stock-based compensation plan.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodForAppreciationOfStockPrice
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the period over which the remainder of the award vests based on continued employment with the company.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsRemainingVestingPeriod
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the term for which the stock-based compensation program will be in force.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsTermOfCompensationProgram
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Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

Represents the value of awards to be earned expressed as percentage of the outperformance amount in excess of the minimum percentage of return which the stockholders are required to achieve for awards to be granted.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsValueOfAwardsToBeEarnedAsPercentageOfExcessOverPerformanceCriteriaOfMinimumReturnOnEquity
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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

Represents the price at which the employees can purchase the shares of common stock of the entity under stock-based compensation plans. Such price is expressed as a percentage of lesser of market value of the shares on the first day or the last day of the offering period under that plan.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardPurchasePriceAsPercentageOfMarketValueOfCommonStock
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Data Type:	num:percentItemType
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Period Type:	instant

Represents the expense recognized during the period arising from equity-based compensation arrangements (for example, shares of stock, unit, stock options or other equity instruments) with employees, directors and certain consultants qualifying for treatment as employees.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 1

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-Name Statement of Financial Accounting Standard (FAS)

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-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

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Number of common stock held in a trust that has been set up specifically to accumulate stock for the sole purpose of distribution to participating employees but not yet earned.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Statement of Position (SOP)

-Number 93-6

-Paragraph 14

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Description of the period of time over which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, which may be expressed in a variety of ways (for example, in years, month and year).

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Description of award terms as to how many shares or portion of an award are no longer contingent on satisfaction of either a service condition, market condition or a performance condition, thereby giving the employee the legal right to convert the award to shares, to sell the shares, and be entitled to the cash proceeds of such sale. For example, vesting may be expressed as being 25 percent of the shares under option on each anniversary of the grant date.

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Equity-based compensation cost during the period with respect to the award, which will be recognized in income (as well as the total recognized tax benefit) or capitalized as part of the cost of an asset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

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-Name Accounting Standards Codification

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The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

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The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(a)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Details

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The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-Section 50

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