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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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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.

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

No definition available.

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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 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.

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Represents the percentage of awards earned, vested on December 17, 2012.

No definition available.

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Represents the percentage of awards earned which will be vesting on August 31, 2014.

No definition available.

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Represents the percentage of awards earned which will be vesting on August 31, 2015.

No definition available.

Name:	slg_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPercentageOfAwardsVestingOnAugust312015
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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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Period Type:	instant

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

No definition available.

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Data Type:	xbrli:durationItemType
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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.

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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

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5047-113901

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph 64

-Subparagraph b

-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.

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

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-Paragraph A240

-Subparagraph g(1)

-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.

Reference 6: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 14

-Section F

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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

-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.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

-SubTopic 40

-Section 25

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=6418455&loc=d3e16701-113920

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Represents the compensation cost capitalized during the period arising from equity-based compensation arrangements (for example, shares of stock, units, 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 Statement of Financial Accounting Standard (FAS)

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-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.

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 718

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-Paragraph 2

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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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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 Accounting Standards Codification

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (c)(2)(i)-(ii)

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 123R

-Paragraph A240

-Subparagraph b(2)(b)

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-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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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Details

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Data Type:	xbrli:stringItemType
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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

-Topic 718

-SubTopic 10

-Section 50

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6415400&loc=d3e5070-113901