Investments - Additional Information (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021 USD ($)	Jun. 30, 2020 USD ($)	Jun. 30, 2021 USD ($) engine aircraft.	Jun. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Net book value of equipment held for operating lease	$ 31,148		$ 31,148		$ 31,753
Equipment Held For Operating Lease
Schedule of Equity Method Investments [Line Items]
Net book value of equipment held for operating lease	$ 1,889,908		$ 1,889,908		$ 1,886,613
WMES
Schedule of Equity Method Investments [Line Items]
Ownership interest	50.00%		50.00%
Number of engines in lease portfolio | engine			36
Number of aircraft in lease portfolio | aircraft.			5
WMES | Equipment Held For Operating Lease
Schedule of Equity Method Investments [Line Items]
Net book value of equipment held for operating lease	$ 280,600		$ 280,600
CASC Willis
Schedule of Equity Method Investments [Line Items]
Ownership interest	50.00%		50.00%
Number of engines in lease portfolio | engine			4
CASC Willis | Equipment Held For Operating Lease
Schedule of Equity Method Investments [Line Items]
Net book value of equipment held for operating lease	$ 49,400		$ 49,400
Other Income | WMES | Asset Management
Schedule of Equity Method Investments [Line Items]
Other sales and revenues	$ 400	$ 300	$ 700	$ 800