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Fair Value Measurements - Additional Information (Details) $ in Thousands | 9 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2019 USD ($) engine | Sep. 30, 2018 engine | Sep. 30, 2018 USD ($) | Sep. 30, 2018 airframe_part_package | Dec. 31, 2018 USD ($) engine | Dec. 31, 2018 USD ($) airframe_part_package
Fair Value Disclosures [Abstract] |  |  |  |  |  |
Fair value of notes receivable | $ 42,200 |  |  |  | $ 200 | $ 200
Fair value of notes payable | 1,246,000 |  |  |  | 1,348,100 | 1,348,100
Derivative [Line Items] |  |  |  |  |  |
Increase in interest expense | (500) |  | $ (200) |  |  |
Increase (decrease) in asset write-down | 11,300 |  | $ 4,800 |  |  |
Remaining book value | $ 19,500 |  |  |  | $ 18,300 | $ 18,300
Number of assets impaired | 10 | 4 |  | 6 | 6 | 6
Interest rate contract |  |  |  |  |  |
Derivative [Line Items] |  |  |  |  |  |
Derivative, notional amount | $ 100,000 |  |  |  | $ 100,000 | $ 100,000
Notional amount, liability | $ 245 |  |  |  |  |
Assets at fair value |  |  |  |  | $ 1,700 | $ 1,700

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