Secured and Unsecured Debt Financings (Details) $ in Thousands		6 Months Ended
	Feb. 29, 2020 Aircraft	Jun. 30, 2020 USD ($) Aircraft	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Number of Aircraft Impaired | Aircraft		20
Outstanding amounts of secured and unsecured term debt financings
Borrowings from secured financings		$ 974,167	$ 1,129,345
Number of Aircraft Financed | Aircraft		36
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 4,137,590	3,932,491
Total secured and unsecured debt financings		$ 5,111,757	5,061,836
Line of Credit | Revolving Credit Facility
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts			150,000
ECA Term Financings | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Number of Aircraft Financed | Aircraft		2
ECA Term Financings | Notes Payable, Other Payables
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		3.60%
Outstanding amounts of secured and unsecured term debt financings
Borrowings from secured financings		$ 45,443	147,644
ECA Term Financings | Minimum | Notes Payable, Other Payables
Outstanding amounts of secured and unsecured term debt financings
Interest rate		3.488%
ECA Term Financings | Maximum | Notes Payable, Other Payables
Outstanding amounts of secured and unsecured term debt financings
Interest rate		3.96%
Bank Financings | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Number of Aircraft Financed | Aircraft		34
Bank Financings | Notes Payable, Other Payables
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate		3.21%
Bank Financings | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Borrowings from secured financings		$ 937,605	993,593
Bank Financings | Minimum | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate		2.1836%
Bank Financings | Maximum | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate		4.55%
2013 Revolving Credit Facility | Line of Credit | Revolving Credit Facility
Outstanding amounts of secured and unsecured term debt financings
Line of Credit Facility, Fair Value of Amount Outstanding		$ 650,000
Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Debt Issuance Cost		(8,881)	(11,892)
Senior Notes Due 2020 | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 0	300,000
Interest rate		7.625%
Senior Notes due 2021 | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 500,000	500,000
Interest rate		5.125%
Senior Notes due 2022 | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 500,000	500,000
Interest rate		5.50%
Senior Notes Due 2023 | 5.00 | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 500,000	500,000
Interest rate		5.00%
Senior Notes Due 2023 | 4.40% | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 650,000	650,000
Interest rate		4.40%
Senior Notes Due 2024 | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 500,000	500,000
Interest rate		4.125%
Floating Rate Term Loan | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate		1.78%
Floating Rate Term Loan | Floating Rate Term Loan
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 215,000	215,000
Floating Rate Term Loan | Minimum | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate		1.7797%
Floating Rate Term Loan | Maximum | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate		1.7797%
Revolving Credit Facility | Minimum | Line of Credit
Outstanding amounts of secured and unsecured term debt financings
Interest rate		1.5564%
Revolving Credit Facility | Maximum | Line of Credit
Outstanding amounts of secured and unsecured term debt financings
Interest rate		1.5709%
Unsecured Debt
Outstanding amounts of secured and unsecured term debt financings
Debt Issuance Cost		$ (27,410)	(32,509)
Senior Notes Due 2026 [Member] | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts		$ 650,000	$ 650,000
Senior Notes Due 2026 [Member] | 4.25% [Member] | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Interest rate		4.25%
South African Airways [Member]
Debt Instrument [Line Items]
Number of Aircraft Impaired | Aircraft	4
Air Knight VIEs | Variable Interest Entity, Primary Beneficiary [Member] | South African Airways [Member] | ECA Term Financings
Debt Instrument [Line Items]
Number of Aircraft Impaired | Aircraft	4