Share Based Compensation - 2018 Equity Incentive Plan (Narratives) (Details)	3 Months Ended
Dec. 31, 2018 shares
Stock options
Share-based Compensation Arrangement by Share-based Payment Award
Share based compensation term (years)	10 years
Vesting Group One
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)	4 years
Award vesting percentage	25.00%
Vesting Group One \| Performance Based
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)	4 years
Award vesting percentage	25.00%
Vesting Group Two
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)	3 years
Vesting Group Two \| Performance Based
Share-based Compensation Arrangement by Share-based Payment Award
Vesting period (years)	3 years
2018 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for distribution (shares)	14,000,000
Increase in reserved shares term	10 years
Periodical increase in authorized shares (percentage)	4.00%
2018 Equity Incentive Plan \| Ordinary shares
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for distribution (shares)	3,281,622
2018 Equity Incentive Plan - New \| Ordinary shares
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for distribution (shares)	3,025,548
2018 Equity Incentive Plan - Shares Available Under 2017 Plan \| Ordinary shares
Share-based Compensation Arrangement by Share-based Payment Award
Shares authorized for distribution (shares)	256,074

Periodical Increase in Authorized Shares for Distribution

No definition available.

Name:	autl_PeriodicalIncreaseinAuthorizedSharesforDistribution
Namespace Prefix:	autl_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Share-based Compensation Arrangement by Share-based Payment Award, Increase In Reserved Shares Term

+ References

No definition available.

+ Details

Name:	autl_SharebasedCompensationArrangementbySharebasedPaymentAwardIncreaseInReservedSharesTerm
Namespace Prefix:	autl_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Period which an employee's right to exercise an award is no longer contingent on satisfaction of either a service condition, market condition or a performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardAwardVestingPeriod1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
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_ShareBasedCompensationArrangementByShareBasedPaymentAwardLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The maximum number of shares (or other type of equity) originally approved (usually by shareholders and board of directors), net of any subsequent amendments and adjustments, for awards under the equity-based compensation plan. As stock or unit options and equity instruments other than options are awarded to participants, the shares or units remain authorized and become reserved for issuance under outstanding awards (not necessarily vested).

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Percentage of vesting of share-based compensation awards.

+ References

+ Details

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

- Definition

Period from grant date that an equity-based award expires, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(2)
-URI http://asc.fasb.org/extlink&oid=109197908&loc=d3e5070-113901

+ Details

Name:	us-gaap_SharebasedCompensationArrangementBySharebasedPaymentAwardExpirationPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_EmployeeStockOptionMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=autl_PerformanceBasedMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=us-gaap_ShareBasedCompensationAwardTrancheTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=autl_A2018EquityIncentivePlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_StatementClassOfStockAxis=autl_OrdinarySharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=autl_A2018EquityIncentivePlanNewMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PlanNameAxis=autl_A2018EquityIncentivePlanSharesAvailableUnder2017PlanMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: