Face (par) amount of debt instrument at time of issuance.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

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- Definition

Period between issuance and maturity of long-term debt, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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- Definition

Notes issues at price as percentage of par.

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- Definition

Number Of Assets Used To Secure Debt

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Debt Obligations - Narrative (Details)	1 Months Ended	3 Months Ended		9 Months Ended
Debt Obligations - Narrative (Details)	Mar. 31, 2020 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Mar. 31, 2020 USD ($)	Mar. 31, 2020	Mar. 31, 2020 engine	Mar. 31, 2020 airframe
Long Term Debt
Loss on debt extinguishment		$ 0	$ 0	$ 4,688,000	$ 220,000
WEST V Series A Notes
Long Term Debt
Fixed rate (as a percent)		3.23%		3.23%
WEST V Series B Notes
Long Term Debt
Fixed rate (as a percent)		4.21%		4.21%
WEST V Series C Notes
Long Term Debt
Fixed rate (as a percent)		6.66%		6.66%
WEST II Series A Notes
Long Term Debt
Fixed rate (as a percent)		5.50%		5.50%
Loss on debt extinguishment	$ 4,700,000
WEST V
Long Term Debt
Number of assets used to secure debt								54	3
WEST V \| WEST V Notes
Long Term Debt
Debt instrument, face amount						$ 366,200,000
WEST V \| WEST V Series A Notes
Long Term Debt
Debt instrument, face amount						303,000,000.0
Fixed rate (as a percent)							3.228%
Debt instrument, term	8 years
Notes issue price, percentage of par	99.99859%
WEST V \| WEST V Series B Notes
Long Term Debt
Debt instrument, face amount						42,100,000
Fixed rate (as a percent)							4.212%
Debt instrument, term	8 years
Notes issue price, percentage of par	99.99493%
WEST V \| WEST V Series C Notes
Long Term Debt
Debt instrument, face amount						$ 21,100,000
Fixed rate (as a percent)							6.657%
Debt instrument, term	8 years
Notes issue price, percentage of par	99.99918%
Assets Under Purchase Agreement With WEST V \| WEST V
Long Term Debt
Number of assets used to secure debt								25	3