Summary of Significant Accounting Policies	3 Months Ended
Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies The significant accounting policies of the Company were described in Note 1 to the audited consolidated financial statements included in the Company’s 2018 Annual Report on Form 10-K (“2018 Form 10-K”). There have been no significant changes in the Company’s significant accounting policies for the three months ended March 31, 2019, except as disclosed in Note 1(d). (a) Basis of Presentation The accompanying Unaudited Condensed Consolidated Financial Statements of the Company have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and in accordance with the rules and regulations of the Securities and Exchange Commission. Therefore, they do not include all information and footnotes normally included in annual consolidated financial statements and should be read in conjunction with the consolidated financial statements and notes thereto included in the 2018 Form 10-K. In the opinion of management, the Unaudited Condensed Consolidated Financial Statements contain all adjustments (consisting principally of normal recurring accruals) necessary for a fair presentation of the condensed consolidated balance sheets, statements of income, statements of comprehensive income, statements of redeemable preferred stock and shareholders' equity and statements of cash flows for such interim periods presented. Additionally, operating results for interim periods are not necessarily indicative of the results that can be expected for a full year. In accordance with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. In preparing these financial statements, management has made its best estimates and judgments of certain amounts included in the financial statements, giving due consideration to materiality. These estimates and judgments are based on historical experience and other assumptions that management believes are reasonable. However, application of these accounting policies involves the exercise of judgment and use of assumptions as to future uncertainties and, as a result, actual results could differ materially from these estimates. The significant estimates made in the accompanying Unaudited Condensed Consolidated Financial Statements include certain assumptions related to goodwill, intangible assets, long-lived assets, equipment held for sale, estimated income taxes and stock-based compensation. Actual results may differ from these estimates under different assumptions or conditions. (b) Adjustments to Prior Period Effective January 1, 2018, the Company adopted Accounting Standards Codification (“ASC”) 606 – “Revenue from Contracts with Customers” and has identified the transfer of engines and airframes from the lease portfolio to the Spare Parts segment for part out as sales to customers in accordance with the ordinary operations of our Spare Parts reportable segment. As such, the Company presents the sale of these assets on a gross basis and have reclassified the three months ended March 31, 2018 gross revenue and costs on sale to the Spare parts and equipment sales and Cost of spare parts and equipment sales line items from the net gain (loss) presentation within the Gain on sale of leased equipment line item. The reclassification resulted in an increase in Spare parts and equipment sales of $6.7 million, a decrease in Gain on sale of leased equipment of $0.1 million and an increase in Cost of spare parts and equipment sales of $6.6 million with no impact to the Company's net income for the three months ended March 31, 2018. The Company's Consolidated Statement of Cash Flows for the three months ended March 31, 2018 were adjusted for this matter by increasing cash flows provided by operating activities by $4.9 million and decreasing cash flows provided by investing activities by a similar amount. (c) Principles of Consolidation The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, including VIEs, where the Company is the primary beneficiary in accordance with consolidation guidance. The Company evaluates all entities in which it has an economic interest firstly to determine whether for accounting purposes the entity is a variable interest entity or voting interest entity. If the entity is a VIE, the Company consolidates the financial statements of that entity if it is the primary beneficiary of the entities’ activities. If the entity is a voting interest entity, the Company consolidates the entity when it has a majority of voting interests. Intercompany transactions and balances have been eliminated in consolidation. (d) Recent Accounting Pronouncements Recent Accounting Pronouncements Adopted by the Company In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” (“ASU 2016-02”) that amends the accounting guidance on leases for both lessees and lessors. The new standard establishes a right-of-use (“ROU”) model that requires a lessee to record an ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The FASB also subsequently issued amendments to the standard, including providing an additional and optional transition method to adopt the new standard, as well as certain practical expedients related to land easements and lessor accounting. The accounting standard update originally required the use of a modified retrospective approach reflecting the application of the standard to leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements with the option to elect certain practical expedients. A subsequent amendment to the standard provided an additional and optional transition method that allowed entities to initially apply the new leases standard at the adoption date and recognize a cumulative effect adjustment to the opening balance of retained earnings in the period of adoption. Consequently, an entity’s reporting for the comparative periods presented in the financial statements in which it adopted the new leases standard would continue to be in accordance with ASC Topic 840 if the optional transition method is elected. The Company adopted the standard using the optional transition method with no restatement of comparative periods and a cumulative effect adjustment recognized as of the date of adoption. Adoption of the new standard resulted in the recording of ROU assets and lease liabilities of approximately $4.5 million and $4.3 million, respectively, as of January 1, 2019. The cumulative effect adjustment to retained earnings as of January 1, 2019 was $0.2 million. The standard did not materially impact our consolidated financial statements. As part of the implementation process, the Company assessed its lease arrangements and evaluated practical expedients and accounting policy elections to meet the reporting requirements of this standard. The Company also evaluated the changes in controls and processes that were necessary to implement the new standard, and no material changes were required. The new standard provides a number of optional practical expedients in transition. The Company elected the ‘package of practical expedients’ which permitted us not to reassess under the new standard the prior conclusions about lease identification, lease classification, and initial direct costs. The Company did not elect the use-of-hindsight or the practical expedient pertaining to land easements; the latter not being applicable to WLFC. Under ASC 842, a lease is a sales-type lease if any one of five criteria are met, each of which indicate that the lease, in effect, transfers control of the underlying asset to the lessee. If none of those five criteria are met, but two additional criteria are both met, indicating that the lessor has transferred substantially all the risks and benefits of the underlying asset to the lessee, the lease is a direct financing lease. All leases that are not sales-type or direct financing leases are operating leases. Furthermore, the Company will assess on an ongoing basis, the updated guidance provided for sale leaseback transactions and whether failed sale leaseback accounting treatment is triggered. As lessor, the Company's leases remained as operating leases under the new standard. In addition, due to the new standard’s narrowed definition of initial direct costs, the Company expenses as incurred, certain lease origination costs that were previously capitalized as initial direct costs and amortized to expense over the lease term. The new standard also provides practical expedients for an entity’s ongoing accounting. The Company elected the short-term lease recognition exemption for all leases that qualify. As a result, for those leases that qualify, the Company did not recognize ROU assets or lease liabilities, including for existing short-term leases. The Company also elected the practical expedient to not separate lease and non-lease components for the majority of its leases as both lessee and lessor. In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.” The ASU is targeted at simplifying the application of hedge accounting and aims at aligning the recognition and presentation of the effects of hedge instruments and hedge items. This guidance became effective for the Company on January 1, 2019 and it did not result in an adjustment to the opening balance of retained earnings for the Company's existing cash flow hedge. Additionally, the presentation and disclosure aspect of ASU 2017-12 was applied on a prospective basis within Note 6. In June 2018, the FASB issued ASU 2018-07, “Compensation - Stock Compensation (Topic 718): Improvements to Non-employee Share-Based Payment Accounting.” The ASU expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from non-employees. The Company adopted this guidance effective January 1, 2019 and it did not materially impact our consolidated financial statements. Recent Accounting Pronouncements To Be Adopted by the Company In June 2016, the FASB issued ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”). ASU 2016-13 revises the measurement of credit losses for financial assets measured at amortized cost from an incurred loss methodology to an expected loss methodology. ASU 2016-13 affects trade receivables, debt securities, net investment in leases, and most other financial assets that represent a right to receive cash. Additional disclosures about significant estimates and credit quality are also required. In November 2018, the FASB issued ASU 2018-19, “Codification Improvements to Topic 326, Financial Instruments – Credit Losses.” This ASU clarifies that receivables from operating leases are accounted for using the lease guidance and not as financial instruments. The effective date will be the first quarter of fiscal year 2020, with early adoption permitted. The Company is evaluating the potential effects on the consolidated financial statements.

Summary of Significant Accounting Policies

The significant accounting policies of the Company were described in Note 1 to the audited consolidated financial statements included in the Company’s 2018 Annual Report on Form 10-K (“2018 Form 10-K”). There have been no significant changes in the Company’s significant accounting policies for the three months ended March 31, 2019, except as disclosed in Note 1(d).

(a) Basis of Presentation

The accompanying Unaudited Condensed Consolidated Financial Statements of the Company have been prepared in conformity with accounting principles generally accepted in the United States (“GAAP”) for interim financial information and in accordance with the rules and regulations of the Securities and Exchange Commission. Therefore, they do not include all information and footnotes normally included in annual consolidated financial statements and should be read in conjunction with the consolidated financial statements and notes thereto included in the 2018 Form 10-K. In the opinion of management, the Unaudited Condensed Consolidated Financial Statements contain all adjustments (consisting principally of normal recurring accruals) necessary for a fair presentation of the condensed consolidated balance sheets, statements of income, statements of comprehensive income, statements of redeemable preferred stock and shareholders' equity and statements of cash flows for such interim periods presented. Additionally, operating results for interim periods are not necessarily indicative of the results that can be expected for a full year.

In accordance with GAAP, management is required to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting period. In preparing these financial statements, management has made its best estimates and judgments of certain amounts included in the financial statements, giving due consideration to materiality. These estimates and judgments are based on historical experience and other assumptions that management believes are reasonable. However, application of these accounting policies involves the exercise of judgment and use of assumptions as to future uncertainties and, as a result, actual results could differ materially from these estimates. The significant estimates made in the accompanying Unaudited Condensed Consolidated Financial Statements include certain assumptions related to goodwill, intangible assets, long-lived assets, equipment held for sale, estimated income taxes and stock-based compensation. Actual results may differ from these estimates under different assumptions or conditions.

(b) Adjustments to Prior Period

Effective January 1, 2018, the Company adopted Accounting Standards Codification (“ASC”) 606 – “Revenue from Contracts with Customers” and has identified the transfer of engines and airframes from the lease portfolio to the Spare Parts segment for part out as sales to customers in accordance with the ordinary operations of our Spare Parts reportable segment. As such, the Company presents the sale of these assets on a gross basis and have reclassified the three months ended March 31, 2018 gross revenue and costs on sale to the Spare parts and equipment sales and Cost of spare parts and equipment sales line items from the net gain (loss) presentation within the Gain on sale of leased equipment line item. The reclassification resulted in an increase in Spare parts and equipment sales of $6.7 million, a decrease in Gain on sale of leased equipment of $0.1 million and an increase in Cost of spare parts and equipment sales of $6.6 million with no impact to the Company's net income for the three months ended March 31, 2018. The Company's Consolidated Statement of Cash Flows for the three months ended March 31, 2018 were adjusted for this matter by increasing cash flows provided by operating activities by $4.9 million and decreasing cash flows provided by investing activities by a similar amount.

The accompanying consolidated financial statements include the accounts of the Company and its wholly owned subsidiaries, including VIEs, where the Company is the primary beneficiary in accordance with consolidation guidance. The Company evaluates all entities in which it has an economic interest firstly to determine whether for accounting purposes the entity is a variable interest entity or voting interest entity. If the entity is a VIE, the Company consolidates the financial statements of that entity if it is the primary beneficiary of the entities’ activities. If the entity is a voting interest entity, the Company consolidates the entity when it has a majority of voting interests. Intercompany transactions and balances have been eliminated in consolidation.

(d) Recent Accounting Pronouncements

Recent Accounting Pronouncements Adopted by the Company

In February 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-02, “Leases (Topic 842)” (“ASU 2016-02”) that amends the accounting guidance on leases for both lessees and lessors. The new standard establishes a right-of-use (“ROU”) model that requires a lessee to record an ROU asset and a lease liability on the balance sheet for all leases with terms longer than 12 months. Leases will be classified as either finance or operating, with classification affecting the pattern of expense recognition in the income statement. The FASB also subsequently issued amendments to the standard, including providing an additional and optional transition method to adopt the new standard, as well as certain practical expedients related to land easements and lessor accounting.

The accounting standard update originally required the use of a modified retrospective approach reflecting the application of the standard to leases existing at, or entered into after, the beginning of the earliest comparative period presented in the financial statements with the option to elect certain practical expedients. A subsequent amendment to the standard provided an additional and optional transition method that allowed entities to initially apply the new leases standard at the adoption date and recognize a cumulative effect adjustment to the opening balance of retained earnings in the period of adoption. Consequently, an entity’s reporting for the comparative periods presented in the financial statements in which it adopted the new leases standard would continue to be in accordance with ASC Topic 840 if the optional transition method is elected. The Company adopted the standard using the optional transition method with no restatement of comparative periods and a cumulative effect adjustment recognized as of the date of adoption.

Adoption of the new standard resulted in the recording of ROU assets and lease liabilities of approximately $4.5 million and $4.3 million, respectively, as of January 1, 2019. The cumulative effect adjustment to retained earnings as of January 1, 2019 was $0.2 million. The standard did not materially impact our consolidated financial statements.

As part of the implementation process, the Company assessed its lease arrangements and evaluated practical expedients and accounting policy elections to meet the reporting requirements of this standard. The Company also evaluated the changes in controls and processes that were necessary to implement the new standard, and no material changes were required. The new standard provides a number of optional practical expedients in transition. The Company elected the ‘package of practical expedients’ which permitted us not to reassess under the new standard the prior conclusions about lease identification, lease classification, and initial direct costs. The Company did not elect the use-of-hindsight or the practical expedient pertaining to land easements; the latter not being applicable to WLFC.

Under ASC 842, a lease is a sales-type lease if any one of five criteria are met, each of which indicate that the lease, in effect, transfers control of the underlying asset to the lessee. If none of those five criteria are met, but two additional criteria are both met, indicating that the lessor has transferred substantially all the risks and benefits of the underlying asset to the lessee, the lease is a direct financing lease. All leases that are not sales-type or direct financing leases are operating leases. Furthermore, the Company will assess on an ongoing basis, the updated guidance provided for sale leaseback transactions and whether failed sale leaseback accounting treatment is triggered. As lessor, the Company's leases remained as operating leases under the new standard. In addition, due to the new standard’s narrowed definition of initial direct costs, the Company expenses as incurred, certain lease origination costs that were previously capitalized as initial direct costs and amortized to expense over the lease term.

The new standard also provides practical expedients for an entity’s ongoing accounting. The Company elected the short-term lease recognition exemption for all leases that qualify. As a result, for those leases that qualify, the Company did not recognize ROU assets or lease liabilities, including for existing short-term leases. The Company also elected the practical expedient to not separate lease and non-lease components for the majority of its leases as both lessee and lessor.

In August 2017, the FASB issued ASU 2017-12, “Derivatives and Hedging (Topic 815): Targeted Improvements to Accounting for Hedging Activities.” The ASU is targeted at simplifying the application of hedge accounting and aims at aligning the recognition and presentation of the effects of hedge instruments and hedge items. This guidance became effective for the Company on January 1, 2019 and it did not result in an adjustment to the opening balance of retained earnings for the Company's existing cash flow hedge. Additionally, the presentation and disclosure aspect of ASU 2017-12 was applied on a prospective basis within Note 6.

In June 2018, the FASB issued ASU 2018-07, “Compensation - Stock Compensation (Topic 718): Improvements to Non-employee Share-Based Payment Accounting.” The ASU expands the scope of Topic 718 to include share-based payment transactions for acquiring goods and services from non-employees. The Company adopted this guidance effective January 1, 2019 and it did not materially impact our consolidated financial statements.

Recent Accounting Pronouncements To Be Adopted by the Company

In June 2016, the FASB issued ASU 2016-13, “Financial Instruments – Credit Losses (Topic 326) Measurement of Credit Losses on Financial Instruments” (“ASU 2016-13”). ASU 2016-13 revises the measurement of credit losses for financial assets measured at amortized cost from an incurred loss methodology to an expected loss methodology. ASU 2016-13 affects trade receivables, debt securities, net investment in leases, and most other financial assets that represent a right to receive cash. Additional disclosures about significant estimates and credit quality are also required. In November 2018, the FASB issued ASU 2018-19, “Codification Improvements to Topic 326, Financial Instruments – Credit Losses.” This ASU clarifies that receivables from operating leases are accounted for using the lease guidance and not as financial instruments. The effective date will be the first quarter of fiscal year 2020, with early adoption permitted. The Company is evaluating the potential effects on the consolidated financial statements.