Future minimum rental payments in aggregate as of the balance sheet date under operating leases.

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=84164653&loc=d3e41551-112718

+ Details

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

- References

No definition available.

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableAbstract
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Future rental payments receivable within one year of the balance sheet date under an operating lease.

+ References

+ Details

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

- Definition

Future rental payments receivable within the fifth year from the balance sheet date under an operating lease.

+ References

+ Details

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

- Definition

Future rental payments receivable within the fourth year from the balance sheet date under an operating lease.

+ References

+ Details

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

- Definition

Future rental payments receivable within the third year from the balance sheet date under an operating lease.

+ References

+ Details

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

- Definition

Future rental payments receivable within the second year from the balance sheet date under an operating lease.

+ References

+ Details

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

- Definition

Future minimum lease payments receivable under operating leases for periods greater than five years following the balance sheet date.

+ References

+ Details

Name:	us-gaap_OperatingLeasesFutureMinimumPaymentsReceivableThereafter
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of property, by major property class, net of accumulated depreciation, subject to or available for lease as of the balance sheet date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 840
-SubTopic 20
-Section 50
-Paragraph 4
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=84164653&loc=d3e41551-112718

+ Details

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

- Definition

The number of units (items of property) under operating lease arrangements.

+ References

No definition available.

+ Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseNumberOfUnits
Namespace Prefix:	us-gaap_
Data Type:	xbrli:decimalItemType
Balance Type:	na
Period Type:	instant

- Definition

The total amount of lease rent revenue.

+ References

No definition available.

+ Details

Name:	wlfc_LeaseRentRevenue
Namespace Prefix:	wlfc_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the number of geographic regions in which aircraft lessees are domiciled in.

+ References

No definition available.

+ Details

Name:	wlfc_NumberOfGeographicRegionsInWhichAircraftLesseesAreDomiciledIn
Namespace Prefix:	wlfc_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	dei_EntityByLocationAxis=srt_EuropeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=srt_AsiaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=srt_SouthAmericaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=country_US
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=country_MX
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=country_CA
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=us-gaap_MiddleEastMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	dei_EntityByLocationAxis=srt_AfricaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorPropertyClassAxis=wlfc_OffLeaseAndOtherEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=us-gaap_PropertyAvailableForOperatingLeaseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorPropertyClassAxis=wlfc_EnginesAndRelatedEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorPropertyClassAxis=wlfc_OtherLeasedPartsAndEquipmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_MajorPropertyClassAxis=wlfc_AircraftsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=wlfc_MonthToMonthMaturityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=wlfc_YearOfMaturity2019Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=wlfc_YearOfMaturity2020Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=wlfc_YearOfMaturity2021Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=wlfc_YearOfMaturity2022Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=wlfc_YearOfMaturity2023Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertySubjectToOrAvailableForOperatingLeaseAxis=wlfc_YearOfMaturityThereafterMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Equipment Held for Operating Lease (Details) $ in Thousands	12 Months Ended
Equipment Held for Operating Lease (Details) $ in Thousands	Dec. 31, 2018 USD ($) engine item aircraft region	Dec. 31, 2017 USD ($) item aircraft	Dec. 31, 2016 USD ($)
Equipment Held for Lease
Number of geographic regions in which aircraft lessees are domiciled in \| region	8
Lease rent revenue	$ 175,609	$ 130,369	$ 119,895
Net book value of equipment held for operating lease	1,673,135	1,342,571
Minimum future payments under non-cancelable leases
2019	136,549
2020	68,565
2021	44,163
2022	30,017
2023	12,019
Thereafter	7,299
Minimum future payments	298,612
Europe
Equipment Held for Lease
Lease rent revenue	70,842	50,789	44,650
Net book value of equipment held for operating lease	624,913	444,938
Asia
Equipment Held for Lease
Lease rent revenue	40,717	34,169	34,524
Net book value of equipment held for operating lease	368,690	258,501
South America
Equipment Held for Lease
Lease rent revenue	40,100	20,307	13,395
Net book value of equipment held for operating lease	260,095	251,959
United States
Equipment Held for Lease
Lease rent revenue	11,338	11,958	11,504
Net book value of equipment held for operating lease	118,508	111,999
Mexico
Equipment Held for Lease
Lease rent revenue	4,721	5,409	6,251
Net book value of equipment held for operating lease	43,602	61,606
Canada
Equipment Held for Lease
Lease rent revenue	4,585	4,355	4,049
Net book value of equipment held for operating lease	33,795	34,399
Middle East
Equipment Held for Lease
Lease rent revenue	3,286	3,360	3,674
Net book value of equipment held for operating lease	18,792	28,977
Africa
Equipment Held for Lease
Lease rent revenue	20	22	$ 1,848
Net book value of equipment held for operating lease	2,597	2,959
Off-lease and other
Equipment Held for Lease
Net book value of equipment held for operating lease	$ 202,143	$ 147,233
Equipment held for lease Member \| Engines and Related Equipment
Equipment Held for Lease
Number of equipments held for lease	244	225
Equipment held for lease Member \| Other leased parts and equipment
Equipment Held for Lease
Number of equipments held for lease \| item	10	7
Equipment held for lease Member \| Aircrafts
Equipment Held for Lease
Number of equipments held for lease \| aircraft	17	16
Month-to-month leases
Equipment Held for Lease
Net book value of equipment held for operating lease	$ 216,523
Leases expiring 2019
Equipment Held for Lease
Net book value of equipment held for operating lease	588,615
Leases expiring 2020
Equipment Held for Lease
Net book value of equipment held for operating lease	290,882
Leases expiring 2021
Equipment Held for Lease
Net book value of equipment held for operating lease	63,387
Leases expiring 2022
Equipment Held for Lease
Net book value of equipment held for operating lease	165,117
Lease expiring 2023
Equipment Held for Lease
Net book value of equipment held for operating lease	90,490
Leases expiring thereafter
Equipment Held for Lease
Net book value of equipment held for operating lease	$ 55,978