Debt Obligations - Schedule of Notes Payable (Details) - USD ($)	9 Months Ended
	Sep. 30, 2024	May 31, 2024	Dec. 31, 2023
Long Term Debt
Gross amount of debt	$ 2,014,734,000		$ 1,827,059,000
Less: unamortized debt issuance costs and note discounts	(24,279,000)		(24,178,000)
Total debt obligations	$ 1,990,455,000		1,802,881,000
Credit facility at a floating rate of interest of one-month term Secured Overnight Financing Rate (“SOFR”) plus 2.85%, secured by engines, airframes, and loan assets. The facility has a committed amount of $500.0 million at September 30, 2024, which revolves until the maturity date of June 2025.
Long Term Debt
Variable rate (as a percent)	2.85%
Line of credit facility outstanding amount	$ 403,018,000		353,000,000
WEST VII Series A 2023 term notes payable at a fixed rate of interest of 8.00%, maturing in October 2048, secured by engines, airframes, and loan assets
Long Term Debt
Fixed rate (as a percent)	8.00%
Gross amount of debt	$ 361,251,000		406,894,000
WEST VI Series A 2021 term notes payable at a fixed rate of interest of 3.10%, maturing in May 2046, secured by engines, airframes, and loan assets
Long Term Debt
Fixed rate (as a percent)	3.10%
Gross amount of debt	$ 243,325,000		252,986,000
WEST VI Series B 2021 term notes payable at a fixed rate of interest of 5.44%, maturing in May 2046, secured by engines, airframes, and loan assets
Long Term Debt
Fixed rate (as a percent)	5.44%
Gross amount of debt	$ 33,800,000		35,142,000
WEST VI Series C 2021 term notes payable at a fixed rate of interest of 7.39%, maturing in May 2046, secured by engines, airframes, and loan assets
Long Term Debt
Fixed rate (as a percent)	7.39%
Gross amount of debt	$ 10,497,000		12,361,000
WEST V Series A 2020 term notes payable at a fixed rate of interest of 3.23%, maturing in March 2045, secured by engines
Long Term Debt
Fixed rate (as a percent)	3.23%
Gross amount of debt	$ 229,807,000		240,371,000
WEST V Series B 2020 term notes payable at a fixed rate of interest of 4.21%, maturing in March 2045, secured by engines
Long Term Debt
Fixed rate (as a percent)	4.21%
Gross amount of debt	$ 32,013,000		33,485,000
WEST V Series C 2020 term notes payable at a fixed rate of interest of 6.66%, maturing in March 2045, secured by engines
Long Term Debt
Fixed rate (as a percent)	6.66%
Gross amount of debt	$ 8,770,000		10,695,000
WEST IV Series A 2018 term notes payable at a fixed rate of interest of 4.75%, maturing in September 2043, secured by engines
Long Term Debt
Fixed rate (as a percent)	4.75%
Gross amount of debt	$ 202,924,000		212,157,000
WEST IV Series B 2018 term notes payable at a fixed rate of interest of 5.44%, maturing in September 2043, secured by engines
Long Term Debt
Fixed rate (as a percent)	5.44%
Gross amount of debt	$ 27,759,000		29,024,000
WEST III Series A 2017 term notes payable at a fixed rate of interest of 4.69%, maturing in August 2042, secured by engines
Long Term Debt
Fixed rate (as a percent)	4.69%
Gross amount of debt	$ 164,792,000		175,705,000
WEST III Series B 2017 term notes payable at a fixed rate of interest of 6.36%, maturing in August 2042, secured by engines
Long Term Debt
Fixed rate (as a percent)	6.36%
Gross amount of debt	$ 22,126,000		23,592,000
Willis Warehouse Facility LLC (“WWFL”) credit facility at a floating rate of interest of one-month term SOFR, plus 2.25%, maturing in May 2029, secured by engines, airframes, and loan assets
Long Term Debt
Line of credit facility, maximum borrowing capacity		$ 500,000,000
Fixed rate (as a percent)	2.25%
Gross amount of debt	$ 213,845,000		0
Note payable at a fixed rate of interest of 5.00%, maturing in February 2033, secured by an engine
Long Term Debt
Fixed rate (as a percent)	5.00%
Gross amount of debt	$ 20,848,000		0
Note payable at a fixed rate of interest of 4.59%, maturing in November 2032, secured by an engine
Long Term Debt
Fixed rate (as a percent)	4.59%
Gross amount of debt	$ 22,225,000		22,610,000
Note payable at a fixed rate of interest of 4.23%, maturing in June 2032, secured by an engine
Long Term Debt
Fixed rate (as a percent)	4.23%
Gross amount of debt	$ 17,734,000		17,802,000
Note payable at a fixed rate of interest of 3.18%, matured in July 2024, secured by an aircraft
Long Term Debt
Fixed rate (as a percent)	3.18%
Gross amount of debt	$ 0		$ 1,235,000
Revolving credit facility | Credit facility at a floating rate of interest of one-month term Secured Overnight Financing Rate (“SOFR”) plus 2.85%, secured by engines, airframes, and loan assets. The facility has a committed amount of $500.0 million at September 30, 2024, which revolves until the maturity date of June 2025.
Long Term Debt
Line of credit facility, maximum borrowing capacity	$ 500,000,000