Investments in Other Companies (Details) $ / shares in Units, $ in Thousands	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended
	Jan. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)	Jun. 30, 2025 USD ($) shares	Jun. 30, 2024 USD ($)	Jun. 30, 2025 USD ($) item shares	Jun. 30, 2024 USD ($)	Dec. 31, 2024 USD ($) shares	Dec. 31, 2023 shares	Dec. 31, 2022 USD ($) $ / shares shares
Long-term debt			$ 2,496,570		$ 2,496,570		$ 2,672,375
Aircraft maintenance, materials, and repairs			$ 238,885	$ 183,267	447,985	$ 328,682
Other income (loss) net					2,100	(7,400)
Aero Engines, LLC. ("Aero Engines")
Payments to acquire interest in joint venture					$ 26,600
Investment ownership (as a percent)			75.00%		75.00%
Long-term debt			$ 0		$ 0
Proceeds from equity method investment distribution					12,000
Aero Engines, LLC. ("Aero Engines") | Other Assets
Investment balance in other companies			$ 12,100		12,100		23,900
Aero Engines, LLC. ("Aero Engines") | Other expense, net
Company's portion of income (loss) generated by other companies					$ 100
Contour Airlines
Investment ownership (as a percent)		9.90%	25.00%		25.00%			9.90%
Payments to acquire equity method investment	$ 15,100	$ 9,900
Number of Board of Directors seats held | item					1
Total number of Board of Directors seats | item					5
Percentage of Board of Directors seats held			20.00%		20.00%
Aircraft maintenance, materials, and repairs					$ 8,500
Aircraft and collectible years					4 years
Contour Airlines | Other Assets
Investment balance in other companies			$ 22,200		$ 22,200
Contour Airlines | Other expense, net
Company's portion of income (loss) generated by other companies					$ 700
Eve Holdings, Inc. ("Eve")
Warrants to purchase shares | shares			1,500,000		1,500,000				1,500,000
Warrants exercise price (in dollars per share) | $ / shares									$ 0.01
Initial investment									$ 10,000
Realized loss						1,400
Realized gain (loss) on exercise of put options						$ 3,400
Eve Holdings, Inc. ("Eve") | Level 3
Beginning balance					$ 8,160
Unrealized gain					$ 2,130
Fair Value, Net Derivative Asset (Liability), Recurring Basis, Still Held, Unrealized Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]					Other Nonoperating Income (Expense)
Ending balance			$ 10,290		$ 10,290		$ 8,160
Eve Holdings, Inc. ("Eve") | Put option
Shares obtained | shares									1,000,000
Shares sold | shares							399,589	600,411
Shares forfeited | shares								600,411
Eve Holdings, Inc. ("Eve") | Other Assets
Investment balance in other companies			$ 10,300		$ 10,300		$ 8,200
Eve Holdings, Inc. ("Eve") | Class A common stock
Number of shares acquired | shares									1,000,000