Fair Value Measurements - Nonrecurring Basis (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2020 USD ($) engine	Dec. 31, 2020 USD ($) engine	Dec. 31, 2020 USD ($) engine aircraft.	Dec. 31, 2019 USD ($) engine
Assets and (Liabilities) at Fair Value
Write-down of equipment	$ 20,540			$ 18,220
Net book value of equipment held for operating lease	31,753	$ 31,753	$ 31,753	31,520
Equipment held for lease
Assets and (Liabilities) at Fair Value
Write-down of equipment	4,900			6,400
Net book value of equipment held for operating lease	1,886,613	$ 1,886,613	$ 1,886,613	$ 1,650,918
Assets To Be Sold Or Parted Out
Assets and (Liabilities) at Fair Value
Write-down of equipment	15,200
Number of assets impaired		10	2	11
Assets To Be Sold Or Parted Out | Equipment held for lease
Assets and (Liabilities) at Fair Value
Net book value of equipment held for operating lease	$ 37,600	$ 37,600	$ 37,600
Number of engines | engine	21	21	21
Impaired Assets
Assets and (Liabilities) at Fair Value
Write-down of equipment	$ 5,300
Number of assets impaired | engine		7		7
Nonrecurring
Assets and (Liabilities) at Fair Value
Equipment held for lease	20,470			$ 18,132
Equipment held for sale	70			88
Total	20,540			18,220
Write-down of equipment	$ 20,500			18,200
Nonrecurring | Assets To Be Sold Or Parted Out
Assets and (Liabilities) at Fair Value
Write-down of equipment				11,800
Nonrecurring | Impaired Assets
Assets and (Liabilities) at Fair Value
Write-down of equipment				$ 6,400