Summary of Significant Accounting Policies - Loyalty Program (Details) $ in Thousands	2 Months Ended	10 Months Ended	12 Months Ended
	Mar. 12, 2025 USD ($)	Dec. 31, 2025 USD ($)	Dec. 31, 2025 USD ($) arrangement	Dec. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Accounting Policies [Abstract]
Frequent flyer program, number of types of revenue arrangements | arrangement			2
Unrecognized revenue from future FREE SPIRIT award redemptions and the sale of mileage credits		$ 96,400	$ 96,400	$ 101,500
Consideration received from credit card loyalty programs	$ 15,240	59,553		85,812	$ 93,147
Portion of proceeds recognized immediately as marketing component	$ 9,089	$ 35,496		$ 51,220	$ 48,071