ACQUISITION AND DISPOSITION OF REAL ESTATE AND PROPERTIES HELD FOR SALE - Acquisition (Details) (USD $)	3 Months Ended
Mar. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Gross leasable area (in square feet)	298,794akr_GrossLeasableArea
Purchase Price	$ 230,036,000
Assumption of Debt	9,765,000
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net
Land	57,509,000
Buildings and improvements	172,527,000
Total consideration	220,271,000
Core Portfolio
Business Acquisition [Line Items]
Gross leasable area (in square feet)	245,500
Purchase Price	179,000,000
Assumption of Debt	9,765,000
Acquisition costs	600,000
Fund IV
Business Acquisition [Line Items]
Gross leasable area (in square feet)	53,294
Purchase Price	51,036,000
Assumption of Debt	0
Acquisition costs	1,600,000
City Center \| San Fransisco, CA \| Core Portfolio
Business Acquisition [Line Items]
Gross leasable area (in square feet)	205,000
Percent Owned	100.00%
Purchase Price	155,000,000
Assumption of Debt	0
163 Highland Avenue \| Needham, MA \| Core Portfolio
Business Acquisition [Line Items]
Gross leasable area (in square feet)	40,500
Percent Owned	100.00%
Purchase Price	24,000,000
Assumption of Debt	9,765,000
1035 Third Avenue \| New York, NY \| Fund IV
Business Acquisition [Line Items]
Gross leasable area (in square feet)	53,294
Percent Owned	100.00%
Purchase Price	51,036,000
Assumption of Debt	0
Acquisitions In 2014
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net
Land	33,390,000	22,625,000
Buildings and improvements	55,249,000	67,875,000
Acquisition-related intangible assets (in Acquired lease intangibles, net)	4,705,000	0
Acquisition-related intangible liabilities (in Acquired lease intangibles, net)	2,844,000	0
Total consideration	90,500,000	90,500,000
Adjustments [Abstract]
Land	10,765,000
Buildings and improvements	(12,626,000)
Acquisition-related intangible assets (in Acquired lease intangibles, net)	4,705,000
Acquisition-related intangible liabilities (in Acquired lease intangibles, net)	(2,844,000)
Total consideration	$ 0

Business Combination, Provisional Information, Initial Accounting Incomplete, Adjustment, Buildings And Improvements

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Percentage of voting equity interests acquired at the acquisition date in the business combination.

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Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer.

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Amount of liabilities incurred by the acquirer as part of consideration transferred in a business combination.

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Amount of real estate acquired, at the acquisition date.

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Amount recognized as of the acquisition date for the identifiable assets acquired in excess of (less than) the aggregate liabilities assumed.

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