Share Capital - Disclosure of detailed information about options, valuation assumptions (Details)	12 Months Ended
Aug. 31, 2020 CAD ($) Year $ / shares	Aug. 31, 2019 CAD ($) Year $ / shares	Aug. 31, 2018 CAD ($) Year $ / shares
Disclosure of classes of share capital [abstract]
Exercise price \| $ / shares	$ 0.08	$ 0.10	$ 0.12
Closing market price on day preceding date of grant \| $	$ 0.05	$ 0.08	$ 0.12
Risk-free interest rate	1.00%	1.80%	1.88%
Expected life (years) \| Year	3.6	3.3	3.1
Expected volatility	80.00%	63.00%	59.00%
Expected dividend yield \| $	$ 0	$ 0	$ 0
Grant date fair value \| $ / shares	$ 0.02	$ 0.03	$ 0.05
Forfeiture rate	14.00%	15.00%	15.00%

Closing market price on day preceding date of grant

No definition available.

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

- Definition

Forfeiture rate

+ References

No definition available.

+ Details

Name:	avl_DescriptionOfExpectedForfeitureRateShareOptionsGranted
Namespace Prefix:	avl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

The expected volatility of the share price used to calculate the fair value of the share options granted. Expected volatility is a measure of the amount by which a price is expected to fluctuate during a period. The measure of volatility used in option pricing models is the annualised standard deviation of the continuously compounded rates of return on the share over a period of time.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Name IFRS
-Number 2
-IssueDate 2019-01-01
-Paragraph 47
-Subparagraph a
-Clause i
-URI http://eifrs.ifrs.org/eifrs/xifrs-link?type=IFRS&num=2&code=ifrs-tx-2019-en-r&anchor=para_47_a_i&doctype=Standard
-URIDate 2019-03-27

+ Details

Name:	ifrs-full_DescriptionOfExpectedVolatilityShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
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Period Type:	duration

- Definition

The option life of share options granted.

+ References

+ Details

Name:	ifrs-full_DescriptionOfOptionLifeShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	duration

- Definition

The implied yield currently available on zero-coupon government issues of the country in whose currency the exercise price for share options granted is expressed, with a remaining term equal to the expected term of the option being valued (based on the option's remaining contractual life and taking into account the effects of expected early exercise). [Refer: Government [member]]

+ References

+ Details

Name:	ifrs-full_DescriptionOfRiskFreeInterestRateShareOptionsGranted
Namespace Prefix:	ifrs-full_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- References

No definition available.

+ Details

Name:	ifrs-full_DisclosureOfClassesOfShareCapitalAbstract
Namespace Prefix:	ifrs-full_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The exercise price of share options granted.

+ References

+ Details

Name:	ifrs-full_ExercisePriceShareOptionsGranted2019
Namespace Prefix:	ifrs-full_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of an expected dividend used to calculate the fair value of share options granted.

+ References

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average share price used as input to the option pricing model to calculate the fair value of share options granted. [Refer: Option pricing model [member]; Weighted average [member]]

+ References

+ Details

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Namespace Prefix:	ifrs-full_
Data Type:	num:perShareItemType
Balance Type:	na
Period Type:	duration