Long-term Debt (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2023 USD ($) aircraft	Dec. 31, 2020 USD ($)	Dec. 31, 2022 USD ($)
Debt Instrument [Line Items]
Total	$ 3,030,310		$ 3,409,311
Current portion of long-term debt	(447,534)		(442,360)
Long-term portion of unamortized debt issue cost, net	(20,593)		(25,179)
Long-term debt, net of current maturities and debt issue costs	2,562,183		2,941,772
Current portion of long-term debt	447,534		442,360
Current portion of unamortized debt issue cost, net	(3,665)		(3,858)
Current portion of long-term debt, net of debt issue costs	$ 443,869		$ 438,502
Basis spread on variable rate	3.50%
Effective interest rate (as a percent)	4.10%		4.00%
Aggregate amounts of principal maturities of long-term debt
2024	$ 447,534
2025	532,314
2026	510,625
2027	464,280
2028	292,812
Thereafter	782,745
Letters of credit	29,200		$ 29,900
Current borrowing capacity	70,800		70,100
Letters of credit and surety bonds outstanding with various banks and surety institutions	$ 49,100		59,200
E175
Debt Instrument [Line Items]
Number of aircraft delivered | aircraft	2
Purchase of aircraft financed through long-term debt	$ 44,700
Debt instrument, term	12 years
Minimum
Debt Instrument [Line Items]
Interest rate (as a percent)	5.60%
Promissory note
Debt Instrument [Line Items]
Debt instrument, term	8 years
Principal amount	$ 25,000
Treasury Loan Agreement
Debt Instrument [Line Items]
Loan		$ 60,000
Notes payable to banks, due in quarterly installments, plus interest at 2.33% to 5.95% through 2035, secured by aircraft
Debt Instrument [Line Items]
Total	$ 2,302,578		2,604,058
Notes payable to banks, due in quarterly installments, plus interest at 2.33% to 5.95% through 2035, secured by aircraft | Minimum
Debt Instrument [Line Items]
Interest rate (as a percent)	2.33%
Notes payable to banks, due in quarterly installments, plus interest at 2.33% to 5.95% through 2035, secured by aircraft | Maximum
Debt Instrument [Line Items]
Interest rate (as a percent)	5.95%
Notes payable to banks, due in monthly or semi-annual installments, plus interest at 2.90% to 5.94% through 2032, secured by aircraft and engines
Debt Instrument [Line Items]
Total	$ 527,092		604,613
Notes payable to banks, due in monthly or semi-annual installments, plus interest at 2.90% to 5.94% through 2032, secured by aircraft and engines | Minimum
Debt Instrument [Line Items]
Interest rate (as a percent)	2.68%
Notes payable to banks, due in monthly or semi-annual installments, plus interest at 2.90% to 5.94% through 2032, secured by aircraft and engines | Maximum
Debt Instrument [Line Items]
Interest rate (as a percent)	5.94%
Notes payable to U.S. Government, interest due quarterly at 1.00% through 2025 and based on SOFR plus 2.0% from 2025 through 2031, unsecured
Debt Instrument [Line Items]
Interest rate (as a percent)	1.00%
Total	$ 200,640		200,640
Basis spread on variable rate	2.00%
Primarily related to acquisition of aircraft and certain spare engines
Debt Instrument [Line Items]
Total	$ 3,000,000		3,400,000
Line of credit
Aggregate amounts of principal maturities of long-term debt
Maximum borrowing capacity	100,000		100,000
Amount outstanding	$ 0		$ 0