Secured and Unsecured Debt Financings (Details) $ in Thousands	3 Months Ended
	Jun. 30, 2019 USD ($) Aircraft	Mar. 31, 2019 USD ($)	Jul. 15, 2019 USD ($)	Jun. 26, 2019 USD ($) Aircraft	May 01, 2019 USD ($) Aircraft	Dec. 31, 2018 USD ($)
Outstanding amounts of secured and unsecured term debt financings
Borrowings from secured financings	$ 1,214,402					$ 798,457
Number of Aircraft Financed | Aircraft	42
Borrowings from unsecured financings, net of debt issuance costs and discounts	$ 4,277,731					3,962,896
Total secured and unsecured debt financings	$ 5,492,133					4,761,353
Present Value of Redemption Price	100.00%
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						425,000
2018 DBS Revolving Credit Facility | Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Increase (Decrease), Net	$ 20,000	$ 30,000
Outstanding amounts of secured and unsecured term debt financings
Line of Credit Facility, Current Borrowing Capacity	$ 300,000	$ 280,000				250,000
ECA Term Financings | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Number of Aircraft Financed | Aircraft	6
ECA Term Financings | Notes Payable, Other Payables
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	3.58%
Outstanding amounts of secured and unsecured term debt financings
Borrowings from secured financings	$ 169,350					189,080
ECA Term Financings | Minimum | Notes Payable, Other Payables
Outstanding amounts of secured and unsecured term debt financings
Interest rate	3.0153%
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	36
Bank Financings | Notes Payable, Other Payables
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	4.04%
Bank Financings | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Borrowings from secured financings	$ 1,059,092					619,715
Bank Financings | Minimum | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate	3.13%
Bank Financings | Maximum | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate	5.30%
2019 BNP-SG Secured Debt Financing [Member] | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Debt Instrument, Face Amount					$ 320,000
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	$ 0
Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Debt Issuance Cost	(14,040)					(10,338)
Senior Notes Due 2019 [Member] | 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	6.25%
Senior Notes Due 2019 [Member] | Senior Notes due 2019 with 6.25% Interest Rate [Domain] | Senior Notes Due 2019 [Member]
Outstanding amounts of secured and unsecured term debt financings
Interest rate	6.25%
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	$ 300,000					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	3.877%
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					120,000
Floating Rate Term Loan | Minimum | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate	3.877%
Floating Rate Term Loan | Maximum | Notes Payable to Banks
Outstanding amounts of secured and unsecured term debt financings
Interest rate	3.877%
Revolving Credit Facility | Line of Credit
Outstanding amounts of secured and unsecured term debt financings
Interest rate	0.00%
Unsecured Debt
Outstanding amounts of secured and unsecured term debt financings
Debt Issuance Cost	$ (37,269)					(32,104)
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					$ 0
Senior Notes Due 2026 [Member] | 4.25% [Member] | Senior Notes
Outstanding amounts of secured and unsecured term debt financings
Interest rate	4.25%
2019 NAB Secured Debt Financing [Member] | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Interest rate				3.14%
Debt Instrument, Face Amount				$ 40,000
2019 Credit AG Secured Debt Financing [Member] | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Debt Instrument, Face Amount					$ 120,000
Senior 4.25% Notes due 2026 [Member] | 4.25% [Member] | Senior 4.25% Notes due 2026 [Member]
Outstanding amounts of secured and unsecured term debt financings
Borrowings from unsecured financings, net of debt issuance costs and discounts	$ 650,000
Interest rate	4.25%
Debt issue price percent	99.515%
A-320-Neo [Member] | 2019 BNP-SG Secured Debt Financing [Member] | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Total Number of Aircraft Securing Financing | Aircraft					8,000
A-320-Neo [Member] | 2019 Credit AG Secured Debt Financing [Member] | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Total Number of Aircraft Securing Financing | Aircraft					3,000
B-737-800 [Member] | 2019 NAB Secured Debt Financing [Member] | Secured Debt
Outstanding amounts of secured and unsecured term debt financings
Total Number of Aircraft Securing Financing | Aircraft				2
Debt Instrument, Redemption, Period One [Member] | Senior 4.25% Notes due 2026 [Member]
Outstanding amounts of secured and unsecured term debt financings
Debt Instrument, Redemption Price, Percentage	100.00%
Debt Instrument, Redemption, Period One [Member] | Senior 4.25% Notes due 2026 [Member] | 4.25% [Member] | Senior 4.25% Notes due 2026 [Member]
Outstanding amounts of secured and unsecured term debt financings
Debt Instrument, Redemption Price, Percentage of Principal Amount Redeemed	100.00%
Debt Instrument, Basis Spread on Variable Rate	0.35%
Debt Instrument, Redemption, Period Two [Member] | Senior 4.25% Notes due 2026 [Member]
Outstanding amounts of secured and unsecured term debt financings
Debt Instrument, Redemption Price, Percentage	101.00%
Subsequent Event | Senior Notes Due 2019 [Member] | Senior Notes Due 2019 [Member]
Outstanding amounts of secured and unsecured term debt financings
Debt Instrument, Unamortized Premium			$ 7,183