Subsequent Events (Details) - Subsequent event	Jul. 31, 2017 USD ($) engine
WEST III
Subsequent events
Aggregate principal amount	$ 335,700,000
Delivery Term	270 days
Number of aircraft engine | engine	56
Series A Notes
Subsequent events
Aggregate principal amount	$ 293,700,000
Fixed rate (as a percent)	4.69%
Issued price (as a percent)	$ 99.91
Series B Notes
Subsequent events
Aggregate principal amount	$ 42,000,000
Fixed rate (as a percent)	6.36%
Issued price (as a percent)	$ 98.3