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Investments - Additional Information (Details) $ in Thousands | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2020 USD ($) | Jun. 30, 2019 USD ($) | Jun. 30, 2020 USD ($) engine | Jun. 30, 2020 USD ($) aircraft. | Jun. 30, 2020 USD ($) | Jun. 30, 2019 USD ($) engine aircraft.
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Maintenance reserve revenue | $ 29,986 | $ 26,475 |  |  | $ 50,514 | $ 51,825
Number of engines sold | engine |  |  | 0 |  |  | 0
WMES |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership interest | 50.00% |  | 50.00% | 50.00% | 50.00% |
Number of engines in lease portfolio | engine |  |  | 36 |  |  |
Number of aircraft in lease portfolio | aircraft. |  |  |  | 5 |  |
Net book value of equipment held for operating lease | $ 299,600 |  | $ 299,600 | $ 299,600 | $ 299,600 |
Number of aircrafts sold | aircraft. |  |  |  | 0 |  | 5
Proceeds from sale of aircraft |  |  |  |  |  | $ 75,500
Number of engines sold |  |  | 0 | 0 |  |
CASC Willis |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Ownership interest | 50.00% |  | 50.00% | 50.00% | 50.00% |
Number of engines in lease portfolio | engine |  |  | 4 |  |  |
Net book value of equipment held for operating lease | $ 47,500 |  | $ 47,500 | $ 47,500 | $ 47,500 |
Number of aircrafts sold | aircraft. |  |  |  | 0 |  | 0
Number of engines sold | engine |  |  | 0 |  |  | 0
Other Income | WMES | Asset Management |  |  |  |  |  |
Schedule of Equity Method Investments [Line Items] |  |  |  |  |  |
Maintenance reserve revenue | $ 300 | $ 600 |  |  | $ 800 | $ 1,100

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