Subsequent Event (Details) $ in Millions	Mar. 03, 2020	Mar. 03, 2020 engine	Mar. 03, 2020 USD ($)	Mar. 03, 2020 airframe	Dec. 31, 2019 engine
Subsequent Event [Line Items]
Number of assets used to secure debt | engine					2
WEST V | Subsequent Event
Subsequent Event [Line Items]
Number of assets used to secure debt		54		3
Delivery period	270 days
WEST V | WEST V Notes | Subsequent Event
Subsequent Event [Line Items]
Aggregate principal amount			$ 366.2
WEST V | WEST V Series A Notes | Subsequent Event
Subsequent Event [Line Items]
Aggregate principal amount			303.0
Fixed rate (as a percent)	3.228%
Notes issue price, percentage of par	99.99859%
WEST V | WEST V Series B Notes | Subsequent Event
Subsequent Event [Line Items]
Aggregate principal amount			42.1
Fixed rate (as a percent)	4.212%
Notes issue price, percentage of par	99.99493%
WEST V | WEST V Series C Notes | Subsequent Event
Subsequent Event [Line Items]
Aggregate principal amount			$ 21.1
Fixed rate (as a percent)	6.6657%
Notes issue price, percentage of par	99.99918%