Long-Term Debt, Finance Leases, and Other Borrowings - Schedule of Long-term Debt (Parenthetical) (Detail) - USD ($) $ in Millions	3 Months Ended	12 Months Ended
Dec. 31, 2023	Sep. 30, 2023
Revolving Credit Facility Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Eight [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2028	2028
Long term debt interest rate description	quarterly interest based on SOFR plus interest spread at 4.50%
Revolving Credit Facility Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Eight [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	4.50%
Revolving Credit Facility Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Eight [Member] \| Maximum [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Incentive recieved	$ 15
Senior and Subordinated Notes Payable to Secured Parties, Due in Monthly Installments Collateralized by the Underlying Aircraft Through 2027 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2027	2027
Long term debt interest rate description	due in monthly installments, interest based on SOFR plus interest spread at 2.71%
Senior and Subordinated Notes Payable to Secured Parties, Due in Monthly Installments Collateralized by the Underlying Aircraft Through 2027 [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	2.71%
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2028	2028
Long term debt interest rate description	due in semi-annual installments, interest based on SOFR plus interest spread at 4.75% to 6.25%
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member] \| Minimum [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	4.75%
Notes Payable to Secured Parties, Due in Semi Annual Installments Collateralized by the Underlying Aircraft Through 2028 [Member] \| Maximum [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	6.25%
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2028	2028
Long term debt interest rate description	due in quarterly installments, interest based on SOFR plus interest at spread 2.20% to 2.32% for senior note & 4.50% for subordinated note
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member] \| Senior Subordinated Notes [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	4.50%
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member] \| Minimum [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	2.20%
Notes Payable to Secured Parties, Due in Quarterly Installments Collateralized by the Underlying Aircraft Through 2028 [Member] \| Maximum [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member] \| Senior Notes [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	2.32%
Notes Payable to Financial Institution, Due in Monthly Installments Collateralized by the Underlying Equipment, Through 2024 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2024	2024
Long term debt interest rate description	due in monthly installments, interest based on fixed interest of 7.50%, through 2024
Long term debt, basis spread on variable rate	7.50%
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member]
Debt Instrument [Line Items]
Long term debt interest rate description	monthly and/or quarterly interest due from 2022 through 2031
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2022
Other Obligations Due to Financial Institutions, Monthly or Quarterly Collateralized by the Underlying Equipment, Due 2022 Through 2031 [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2031	2031
Notes Payable to Financial Institution, Quarterly, Through 2027 [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2027	2027
Long term debt interest rate description	Notes payable to financial institution, quarterly interest based on SOFR plus interest spread at 3.50%
Notes Payable to Financial Institution, Quarterly, Through 2027 [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	3.50%
Notes Payable To Financial Institution Due In Monthly Installments Collateralized By Underlying Equipment Through Two Thousand Twenty Four [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2024	2024
Long term debt interest rate description	due in monthly installments, interest based on SOFR plus interest spread at 3.10%
Notes Payable To Financial Institution Due In Monthly Installments Collateralized By Underlying Equipment Through Two Thousand Twenty Four [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Long term debt, basis spread on variable rate	3.10%
United Bridge Loan Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Four [Member]
Debt Instrument [Line Items]
Long term debt interest rate description	due in quarterly installments based on SOFR plus interest spread at 4.50%
United Bridge Loan Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Four [Member] \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Debt instrument maturity year	2024	2024
Long term debt, basis spread on variable rate	4.50%

Revolving Credit Facility Quaterly Collateralized By Underlying Equipment And Investments Through Two Thousand Twenty Eight [Member]