Balance Sheet Information - Additional Information (Detail)		1 Months Ended		3 Months Ended		6 Months Ended
	Jan. 31, 2024 USD ($)	Sep. 30, 2021 USD ($) shares	Jul. 31, 2021 USD ($)	Mar. 31, 2024 USD ($)	Mar. 31, 2023 USD ($)	Mar. 31, 2024 USD ($) RotableParts	Mar. 31, 2023 USD ($)	Sep. 30, 2023 USD ($)	Feb. 28, 2022 USD ($)	Feb. 28, 2021 USD ($)
Condensed Balance Sheet Statements Captions [Line Items]
Impairment loss related to the held for sale aircraft						$ 500,000
Depreciation expense				$ 9,800,000	$ 16,500,000	23,100,000	$ 31,600,000
Estimated initial equity warrant asset value										$ 16,400,000
Total net unrealized gain/(loss)				(6,500,000)	2,100,000	(4,000,000)	400,000
Estimated initial warrant asset value									$ 3,200,000
Investments in equity securities				11,397,000		11,397,000		$ 20,320,000
Total realized gain (loss) on equity securities				7,200,000	$ 0	7,200,000	0
Aggregate carrying amount of investments in equity securities				11,400,000		11,400,000		20,300,000
Investments without readily determinable fair value				300,000		300,000		$ 8,800,000
Asset impairment						43,043,000	$ 20,462,000
United Capacity Purchase Agreement [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Realized and unrealized gain (loss) on investment	$ 7,200,000
DHL Fleet [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Impairment loss related to the held for sale aircraft						$ 2,200,000
Number of rotable parts on impairment true-up adjustment | RotableParts						737
Archer Aviation, Inc. [Member] | Level 1 [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Realized and unrealized gain (loss) on investment				(3,400,000)		$ (1,000,000)
Investments in equity securities				10,500,000		10,500,000
VTOL Aircraft, XTI Aerospace, Inc [Member] | Level 1 [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Realized and unrealized gain (loss) on investment				(3,000,000)		(3,000,000)
Investments in equity securities				$ 500,000		$ 500,000
Heart Aerospace Incorporated [Member] | Forward Purchase Contract [Member] | Preferred Stock [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Purchase of preferred stock			$ 5,000,000.0
Initial investment in preferred stock measured at cost			$ 5,000,000
Class A [Member] | Archer Aviation, Inc. [Member]
Condensed Balance Sheet Statements Captions [Line Items]
Stock issued during period, Shares | shares		500,000
Stock issued during period, Value		$ 5,000,000
Total grant date value, Additional warrant to purchase shares		$ 5,600,000