Gain (Loss) on Extinguishment of Debt, Modification and Termination of Derivative Instruments

No definition available.

Name:	art_GainLossOnExtinguishmentOfDebtModificationAndTerminationOfDerivativeInstruments
Namespace Prefix:	art_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=126972273&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126972273&loc=d3e12317-112629

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

+ Details

Name:	us-gaap_GainsLossesOnExtinguishmentOfDebt
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash outflow during the period from the repayment of aggregate short-term and long-term debt. Excludes payment of capital lease obligations.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3291-108585

+ Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=art_TwentyTwentySeniorUnsecuredTermLoanAMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=us-gaap_InterestRateSwapMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_MediumTermNotesMember
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Data Type:	na
Balance Type:
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- Details

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Debt - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended					9 Months Ended
Debt - Narrative (Details) - USD ($) $ in Thousands	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Mar. 31, 2021	Sep. 30, 2020	Sep. 30, 2022	Sep. 30, 2021
Line of Credit Facility [Line Items]
Loss on debt extinguishment and modifications		$ (3,400)				$ (3,410)	$ 0
Total 2020 Senior Unsecured Term Loan A Facility \| Interest rate contracts
Line of Credit Facility [Line Items]
Gain (loss) on extinguishment of debt, modification and termination of derivative instruments	$ 600				$ 600	1,900	$ 2,100
Total 2020 Senior Unsecured Term Loan A Facility \| Term Loans
Line of Credit Facility [Line Items]
Loss on debt extinguishment and modifications			$ (2,900)
Repayments of debt				$ 200,000
Total 2020 Senior Unsecured Term Loan A Facility \| Term Loans \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Loss on debt extinguishment and modifications	$ (300)					$ (300)