Debt - Unsecured Notes Payable (Details)	12 Months Ended
Dec. 31, 2017 USD ($) debtinstrument	Dec. 31, 2016 USD ($)
Debt Instrument [Line Items]
Number of instruments held \| debtinstrument	6
Letters of credit, outstanding amount	$ 19,700,000	$ 11,300,000
Unsecured Notes Payable \| Unsecured Debt
Debt Instrument [Line Items]
Debt available balance	70,300,000	9,900,000
Fund IV \| Letter of Credit \| Unsecured Debt
Debt Instrument [Line Items]
Letters of credit, outstanding amount	7,400,000	0
Fund IV \| Bridge facility \| Unsecured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity	41,812,000
Long-term line of credit, noncurrent	40,800,000	40,100,000
Remaining borrowing capacity	1,000,000	0
Fund IV \| Subscription Line \| Unsecured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity	21,500,000.0
Long-term line of credit, noncurrent	0	94,500,000
Remaining borrowing capacity	14,100,000	$ 5,500,000
Fund V \| Subscription Line \| Unsecured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity	150,000,000.0
Long-term line of credit, noncurrent	103,300,000
Remaining borrowing capacity	46,700,000
Fund II \| Term Loan Maturing In September 2020 \| Secured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity	40,000,000.0
Long-term line of credit, noncurrent	31,500,000
Remaining borrowing capacity	$ 8,500,000
LIBOR \| Fund V \| Subscription Line \| Unsecured Debt
Debt Instrument [Line Items]
Basis spread on variable rate	1.60%
LIBOR \| Fund II \| Term Loan Maturing In September 2020 \| Secured Debt
Debt Instrument [Line Items]
Basis spread on variable rate	1.40%
Core Portfolio
Debt Instrument [Line Items]
Number of instruments held \| debtinstrument	3
Core Portfolio \| $300 Million Term Loan \| Unsecured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 300,000,000.0
Core Portfolio \| $150 Million Term Loan \| Unsecured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity	150,000,000.0
Core Portfolio \| $50 Million Term Loan \| Unsecured Debt
Debt Instrument [Line Items]
Maximum borrowing capacity	$ 50,000,000.0
Number of instruments held	3

Debt Instruments, Number Of Instruments Held

No definition available.

Name:	akr_DebtInstrumentsNumberOfInstrumentsHeld
Namespace Prefix:	akr_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

+ References

+ Details

Name:	us-gaap_DebtInstrumentUnusedBorrowingCapacityAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the noncurrent portion of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 45
-Paragraph 13
-URI http://asc.fasb.org/extlink&oid=99376301&loc=d3e1314-112600

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 10
-Section 45
-Paragraph 14
-URI http://asc.fasb.org/extlink&oid=99376301&loc=d3e1336-112600

+ Details

Name:	us-gaap_LongTermLineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant