SCHEDULE IV - MORTGAGE LOANS ON REAL ESTATE - Reconciliation of Loans on Real Estate (Details) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Movement in Mortgage Loans on Real Estate [Roll Forward]
Balance at beginning of year	$ 276,163	$ 147,188	$ 102,286
Additions	11,371	171,794	48,500
Disposition of air rights through issuance of notes	0	0	29,539
Repayments	(32,000)	(42,819)	(15,984)
Conversion to real estate through receipt of deed or through foreclosure	(101,705)	0	(13,386)
Other	0	0	(3,767)
Balance at end of year	$ 153,829	$ 276,163	$ 147,188

Mortgage Loans on Real Estate, Cost of Mortgages Sold or Foreclosures

No definition available.

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Namespace Prefix:	akr_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Total carrying amount of mortgage loans as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.6)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of principal collected on mortgage loans on real estate during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 948
-SubTopic 310
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-29.6)
-URI http://asc.fasb.org/extlink&oid=6589523&loc=d3e617274-123014

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 205
-SubTopic 10
-Section S99
-Paragraph 6
-Subparagraph (SX 210.5-04.(c) Schedule IV)
-URI http://asc.fasb.org/extlink&oid=27047687&loc=d3e5864-122674

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Total amount of new mortgage loans on real estate during the reporting period.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Total amount of additions to mortgage loans other than new loans during the reporting period.

+ References

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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- Definition

The amount of reductions in principal on mortgage loans other than foreclosures, costs of mortgages sold, and amortization of premium during the reporting period.

+ References

+ Details

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- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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