Long-term Debt (Details) $ in Thousands	6 Months Ended
	Jun. 30, 2025 USD ($) aircraft	Dec. 31, 2024 USD ($)
Debt Instrument [Line Items]
Current portion of long-term debt	$ 493,874	$ 539,061
Current portion of unamortized debt issue cost, net	(3,338)	(3,472)
Current portion of long-term debt, net of debt issue costs	490,536	535,589
Long-term debt, net of current maturities	2,020,771	2,153,558
Long-term portion of unamortized debt issue cost, net	(14,737)	(16,772)
Long-term debt, net of current maturities and debt issue costs	2,006,034	2,136,786
Total long-term debt (including current portion)	2,514,645	2,692,619
Total unamortized debt issue cost, net	(18,075)	(20,244)
Total long-term debt, net of debt issue costs	$ 2,496,570	2,672,375
Effective interest rate (as a percent)	4.30%
Basis spread on variable rate	3.50%
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]	us-gaap:SecuredOvernightFinancingRateSofrMember
Letters of credit and surety bonds
Debt Instrument [Line Items]
Letters of credit and surety bonds outstanding with various banks and surety institutions	$ 49,100	$ 47,100
Letters of credit
Debt Instrument [Line Items]
Amount outstanding	25,000
Unsecured debt payable to U.S. Treasury
Debt Instrument [Line Items]
Total long-term debt, net of debt issue costs	200,600
Unsecured debt payable to U.S. Treasury at fixed annual interest rate
Debt Instrument [Line Items]
Total long-term debt, net of debt issue costs	$ 138,600
Interest rate (as a percent)	1.00%
Basis spread on variable rate	2.00%
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]	us-gaap:SecuredOvernightFinancingRateSofrMember
Unsecured debt payable to U.S. Treasury at variable interest rate
Debt Instrument [Line Items]
Total long-term debt, net of debt issue costs	$ 62,000
Basis spread on variable rate	2.00%
Debt Instrument, Variable Interest Rate, Type [Extensible Enumeration]	us-gaap:SecuredOvernightFinancingRateSofrMember
Primarily related to acquisition of aircraft and certain spare engines
Debt Instrument [Line Items]
Total long-term debt (including current portion)	$ 2,500,000
Total long-term debt, net of debt issue costs	2,300,000
Line of credit
Debt Instrument [Line Items]
Maximum borrowing capacity	100,000
Amount outstanding	0
Current borrowing capacity	$ 75,000
Basis spread on variable rate	3.50%
E175
Debt Instrument [Line Items]
Number of aircraft delivered | aircraft	2
Purchase of aircraft financed through long-term debt	$ 47,100
Debt instrument, term	12 years