Number of joint ventures the company participates under the agreement with co-investment vehicle.

No definition available.

Name:	al_AgreementWithCoInvestmentVehicleNumberOfJointVenturesCompanyParticipated
Namespace Prefix:	al_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of unfunded commitment for equity method investment.

+ References

No definition available.

+ Details

Name:	al_EquityMethodInvestmentUnfundedCommitment
Namespace Prefix:	al_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of long-lived assets that are being held for sale.

+ References

No definition available.

+ Details

Name:	al_LongLivedAssetsHeldForSale
Namespace Prefix:	al_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

This element represents the aggregate cost of investments accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.12)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

Name:	us-gaap_EquityMethodInvestmentAggregateCost
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(1)
-URI http://asc.fasb.org/extlink&oid=114001798&loc=d3e33918-111571

+ Details

Name:	us-gaap_EquityMethodInvestmentOwnershipPercentage
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of investment in equity security without readily determinable fair value.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 321
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=116654751&loc=SL75117539-209714

+ Details

Name:	us-gaap_EquitySecuritiesWithoutReadilyDeterminableFairValueAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByParent
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Number of aircraft operated by the carrier.

+ References

No definition available.

+ Details

Name:	us-gaap_NumberOfAircraftOperated
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of aircraft sold by the entity during the period.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertyPlantAndEquipmentNumberOfAircraftSold
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
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_ScheduleOfEquityMethodInvestmentsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=al_BlackbirdCapitalILlcAndBlackbirdCapitalIiLlcMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=al_BlackbirdCapitalILLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=al_BlackbirdCapitalIILLCMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=al_ThunderboltAircraftLeaseLimitedIiMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongLivedAssetsHeldForSaleByAssetTypeAxis=al_AircraftHeldForSaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=srt_ScenarioForecastMember
Namespace Prefix:
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Investments (Details)	3 Months Ended	9 Months Ended	12 Months Ended
Investments (Details)	Dec. 31, 2019 aircraft	Sep. 30, 2019 USD ($) aircraft item	Dec. 31, 2018 USD ($) aircraft	Aug. 01, 2018 USD ($)
Blackbird I and Blackbird II
Investments
Number of joint ventures \| item		2
Equity method investment		$ 45,900,000	$ 40,600,000
Blackbird Capital I
Investments
Percentage of equity ownership		9.50%
Blackbird Capital II
Investments
Percentage of equity ownership		9.50%
Total unfunded commitment		$ 30,500,000
Thunderbolt II
Investments
Non-controlling interest (as a percent)				5.10%
Cost Method Investments			$ 5,400,000
Aircraft Held For Sale
Investments
Number of aircraft sold or agreed to be sold \| aircraft	6	6	6
Aircraft Held For Sale \| Thunderbolt II
Investments
Number of aircraft sold or agreed to be sold \| aircraft		3
Long-lived assets held for sale				$ 18
Forecast \| Aircraft Held For Sale \| Thunderbolt II
Investments
Number of aircraft \| aircraft	3