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

No definition available.

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)(1)
-URI https://asc.fasb.org/extlink&oid=123466204&loc=SL6031897-161870

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI https://asc.fasb.org/extlink&oid=126734703&loc=d3e572229-122910

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI https://asc.fasb.org/extlink&oid=126897435&loc=d3e534808-122878

+ Details

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
-Paragraph 1B
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123466505&loc=SL123495323-112611

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI https://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- 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
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Period Type:	duration

- Details

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- Details

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- Details

Name:	us-gaap_VariableRateAxis=art_SecuredOvernightFinancingAdjustmentRateMember
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- Details

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- Details

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Debt - Schedule of Senior Unsecured Term Loans (Details) $ in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2023 USD ($)	Mar. 31, 2023 CAD ($)	Dec. 31, 2022 USD ($)	Dec. 31, 2022 CAD ($)
Debt Instrument [Line Items]
Contractual Interest Rate	0.94%	0.94%	0.95%	0.95%
Carrying Amount	$ 3,203,375		$ 3,082,377
2022/2020 Senior Unsecured Term Loan A-1 \| Term Loans
Debt Instrument [Line Items]
Contractual Interest Rate	0.94%	0.94%	0.95%	0.95%
Carrying Amount	$ 375,000		$ 375,000
2022/2020 Senior Unsecured Term Loan A-1 \| Term Loans \| Secured Overnight Financing Adjustment Rate
Debt Instrument [Line Items]
Applicable interest rate	0.10%
2022/2020 Senior Unsecured Term Loan A-1 \| Term Loans \| U.S. dollar
Debt Instrument [Line Items]
Carrying Amount	$ 375,000		$ 375,000
2022/2020 Senior Unsecured Term Loan A-2 \| Term Loans
Debt Instrument [Line Items]
Contractual Interest Rate	0.94%	0.94%	0.95%	0.95%
Carrying Amount		$ 250,000		$ 250,000
2022/2020 Senior Unsecured Term Loan A-2 \| Term Loans \| Canadian dollar
Debt Instrument [Line Items]
Carrying Amount	$ 184,950		$ 184,450
Delayed Draw Tranche A-3 \| Term Loan Delayed Draw Facility
Debt Instrument [Line Items]
Carrying Amount	270,000	$ 270,000	270,000	$ 270,000
Senior Unsecured Term Loans \| Term Loans
Debt Instrument [Line Items]
Carrying Amount	$ 829,950		$ 829,450