Debt Obligations - Schedule of Notes Payable (Details) - USD ($)	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Jun. 30, 2019
Long Term Debt [Line Items]
Long-term debt outstanding	$ 1,809,620,000	$ 1,712,886,000
Less: unamortized debt issuance costs	(19,356,000)	(19,133,000)
Total debt obligations	1,790,264,000	1,693,753,000
Credit facility at a floating rate of interest of one-month LIBOR plus 1.75% at December 31, 2021, secured by engines. The facility has a committed amount of $1.0 billion at December 31, 2021, which revolves until the maturity date of June 2024
Long Term Debt [Line Items]
Line of credit facility outstanding amount	$ 590,000,000	777,000,000
WEST VI Series A 2021 term notes payable at a fixed rate of interest of 3.10%, maturing in May 2046, secured by engines
Long Term Debt [Line Items]
Fixed rate	3.10%
Long-term debt outstanding	$ 273,723,000	0
WEST VI Series B 2021 term notes payable at a fixed rate of interest of 5.44%, maturing in May 2046, secured by engines
Long Term Debt [Line Items]
Fixed rate	5.44%
Long-term debt outstanding	$ 38,022,000	0
WEST VI Series C 2021 term notes payable at a fixed rate of interest of 7.39%, maturing in May 2046, secured by engines
Long Term Debt [Line Items]
Fixed rate	7.39%
Long-term debt outstanding	$ 18,158,000	0
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 [Line Items]
Fixed rate	3.23%
Long-term debt outstanding	$ 272,909,000	286,863,000
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 [Line Items]
Fixed rate	4.21%
Long-term debt outstanding	$ 38,004,000	39,855,000
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 [Line Items]
Fixed rate	6.66%
Long-term debt outstanding	$ 16,342,000	19,043,000
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 [Line Items]
Fixed rate	4.75%
Long-term debt outstanding	$ 262,260,000	277,481,000
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 [Line Items]
Fixed rate	5.44%
Long-term debt outstanding	$ 38,885,000	39,640,000
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 [Line Items]
Fixed rate	4.69%
Long-term debt outstanding	$ 223,815,000	227,138,000
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 [Line Items]
Fixed rate	6.36%
Long-term debt outstanding	$ 32,195,000	32,481,000
Note payable at three-month LIBOR plus a margin ranging from 1.85% to 2.50%, repaid in May 2021, secured by engines
Long Term Debt [Line Items]
Long-term debt outstanding	$ 0	6,138,000
Note payable at a fixed rate of interest of 3.18%, maturing in July 2024, secured by an aircraft
Long Term Debt [Line Items]
Fixed rate	3.18%
Long-term debt outstanding	$ 5,307,000	$ 7,247,000
Revolving credit facility | Credit facility at a floating rate of interest of one-month LIBOR plus 1.75% at December 31, 2021, secured by engines. The facility has a committed amount of $1.0 billion at December 31, 2021, which revolves until the maturity date of June 2024
Long Term Debt [Line Items]
Line of credit facility, maximum borrowing capacity	$ 1,000,000,000		$ 1,000,000,000
LIBOR | Credit facility at a floating rate of interest of one-month LIBOR plus 1.75% at December 31, 2021, secured by engines. The facility has a committed amount of $1.0 billion at December 31, 2021, which revolves until the maturity date of June 2024
Long Term Debt [Line Items]
Variable rate spread	1.75%
LIBOR | Note payable at three-month LIBOR plus a margin ranging from 1.85% to 2.50%, repaid in May 2021, secured by engines | Minimum
Long Term Debt [Line Items]
Variable rate spread	1.85%
LIBOR | Note payable at three-month LIBOR plus a margin ranging from 1.85% to 2.50%, repaid in May 2021, secured by engines | Maximum
Long Term Debt [Line Items]
Variable rate spread	2.50%