Fair Value Measurements (Details 2) - USD ($) $ in Thousands	Dec. 31, 2019	Dec. 31, 2018
Secured Debt | Significant Other Observable Inputs (Level 2) | Reported Value Measurement | DBJ Term Loan
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	$ 215,000	$ 120,000
Secured Debt | Significant Other Observable Inputs (Level 2) | Reported Value Measurement | ECA Term Financings
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	147,644	189,080
Secured Debt | Significant Other Observable Inputs (Level 2) | Reported Value Measurement | Bank Financings
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	993,593	619,715
Secured Debt | Significant Other Observable Inputs (Level 2) | Estimate of Fair Value Measurement | DBJ Term Loan
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	215,000	120,000
Secured Debt | Significant Other Observable Inputs (Level 2) | Estimate of Fair Value Measurement | ECA Term Financings
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	150,805	190,216
Secured Debt | Significant Other Observable Inputs (Level 2) | Estimate of Fair Value Measurement | Bank Financings
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	1,010,482	623,604
Unsecured Debt | Quoted Prices In Active Markets for Identical Assets (Level 1) | Reported Value Measurement | Revolving Credit Facility
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	150,000	425,000
Unsecured Debt | Quoted Prices In Active Markets for Identical Assets (Level 1) | Reported Value Measurement | Senior Notes
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	3,600,000	3,450,000
Unsecured Debt | Quoted Prices In Active Markets for Identical Assets (Level 1) | Estimate of Fair Value Measurement | Senior Notes
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Debt Instrument, Fair Value Disclosure	$ 3,787,268	$ 3,446,826