Investments - Additional Information (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2021 USD ($) engine aircraft.	Mar. 31, 2020 USD ($)	Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Net book value of equipment held for operating lease	$ 31,169		$ 31,753
Assets Leased to Others
Schedule of Equity Method Investments [Line Items]
Net book value of equipment held for operating lease	$ 1,887,884		$ 1,886,613
WMES
Schedule of Equity Method Investments [Line Items]
Ownership interest	50.00%
Number of engines in lease portfolio | engine	36
Number of aircraft in lease portfolio | aircraft.	5
WMES | Assets Leased to Others
Schedule of Equity Method Investments [Line Items]
Net book value of equipment held for operating lease	$ 285,000
CASC Willis
Schedule of Equity Method Investments [Line Items]
Ownership interest	50.00%
Number of engines in lease portfolio | engine	4
CASC Willis | Assets Leased to Others
Schedule of Equity Method Investments [Line Items]
Net book value of equipment held for operating lease	$ 49,700
Other Income | WMES | Asset Management
Schedule of Equity Method Investments [Line Items]
Maintenance reserve revenue	$ 300	$ 500