Derivative, Amount of Hedged Liability

No definition available.

Name:	art_DerivativeAmountofHedgedLiability
Namespace Prefix:	art_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Derivative, Notational Amount, Percentage

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

+ References

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-Publisher FASB
-Name Accounting Standards Codification
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-SubTopic 30
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+ Details

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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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Period Type:	duration

- Definition

Nominal or face amount used to calculate payment on derivative.

+ References

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+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Period the derivative contract is outstanding, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Amount before tax of foreign currency transaction realized and unrealized gain (loss) recognized in the income statement.

+ References

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+ Details

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Balance Type:	credit
Period Type:	duration

- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

+ References

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Derivative Financial Instruments - Narrative (Details) $ in Thousands, $ in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2018 USD ($)	Sep. 30, 2019 AUD ($)	Sep. 30, 2019 NZD ($)
Derivative [Line Items]
Interest expense	$ 24,907	$ 22,834	$ 70,581	$ 70,258
Foreign currency exchange (loss) gain, net	(43)	$ 734	$ (66)	$ 2,926
Interest Rate Swap
Derivative [Line Items]
Derivative agreement term			5 years
Gain (loss) to be reclassified in next twelve months			$ (100)
Foreign Exchange Forward
Derivative [Line Items]
Gain (loss) to be reclassified in next twelve months			300
Foreign Exchange Forward \| Intercompany Loan \| Australian Intercompany Loan
Derivative [Line Items]
Receivable hedged					$ 153.5
Foreign Exchange Forward \| Intercompany Loan \| New Zealand Intercompany Loan
Derivative [Line Items]
Receivable hedged						$ 37.5
January 2019 Agreement \| Interest Rate Swap
Derivative [Line Items]
Notational amount	$ 100,000		$ 100,000
Notational amount, percentage	21.00%		21.00%		21.00%	21.00%
August 2019 Agreement \| Interest Rate Swap
Derivative [Line Items]
Notational amount	$ 225,000		$ 225,000
Notational amount, percentage	47.00%		47.00%		47.00%	47.00%