Secured and Unsecured Debt Financings (Details 1) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Debt Instrument [Line Items]
Borrowings from unsecured financings, net of debt issuance costs and discounts	$ 4,435,107	$ 3,932,491
Line of Credit Facility, Remaining Borrowing Capacity	$ 450,000
Notes Payable, Other Payables | ECA Term Financings
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	3.61%
Notes Payable, Other Payables | Bank Financings
Debt Instrument [Line Items]
Debt, Weighted Average Interest Rate	3.52%
Senior Notes | Senior Notes Due 2024
Debt Instrument [Line Items]
Interest rate	4.125%
Borrowings from unsecured financings, net of debt issuance costs and discounts	$ 500,000	500,000
Senior Notes | Senior Notes Due 2020
Debt Instrument [Line Items]
Interest rate	7.625%
Borrowings from unsecured financings, net of debt issuance costs and discounts	$ 300,000	300,000
Senior Notes | Senior Notes due 2021
Debt Instrument [Line Items]
Interest rate	5.125%
Borrowings from unsecured financings, net of debt issuance costs and discounts	$ 500,000	500,000
Senior Notes | Senior Notes due 2022
Debt Instrument [Line Items]
Interest rate	5.50%
Borrowings from unsecured financings, net of debt issuance costs and discounts	$ 500,000	500,000
Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Borrowings from unsecured financings, net of debt issuance costs and discounts		150,000
Line of Credit | 2013 Revolving Credit Facility | Revolving Credit Facility
Debt Instrument [Line Items]
Line of Credit Facility, Fair Value of Amount Outstanding	$ 650,000
Maximum | Notes Payable, Other Payables | ECA Term Financings
Debt Instrument [Line Items]
Interest rate	3.96%
Maximum | Notes Payable to Banks | Bank Financings
Debt Instrument [Line Items]
Interest rate	4.55%
Maximum | Line of Credit | Revolving Credit Facility
Debt Instrument [Line Items]
Interest rate	2.4591%
4.40% | Senior Notes | Senior Notes Due 2023
Debt Instrument [Line Items]
Interest rate	4.40%
Borrowings from unsecured financings, net of debt issuance costs and discounts	$ 650,000	$ 650,000