Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Statement of Cash Flows [Abstract]
Net cash provided by (used in) Operating Activities	$ (173,482)	$ 456,895
Cash flows from Investing Activities:
Additions to property and equipment, including pre-delivery payments	(101,775)	(280,288)
Proceeds from the purchase assignment and sale leaseback	114,000	0
Proceeds from the disposition of aircraft related equipment	0	9,045
Purchases of investments	(408,955)	(265,705)
Sales of investments	214,469	267,464
Other	0	(6,275)
Net cash used in investing activities	(182,261)	(275,759)
Cash flows from Financing Activities:
Long-term borrowings	602,264	227,889
Repayments of long-term debt and finance lease obligations	(64,686)	(95,356)
Dividend payments	(5,514)	(17,206)
Debt issuance costs	(3,506)	(1,162)
Repurchases of common stock	(7,510)	(50,690)
Other	(1,359)	(1,026)
Net cash provided by financing activities	519,689	62,449
Net increase in cash and cash equivalents	163,946	243,585
Cash, cash equivalents, and restricted cash - Beginning of Period	373,056	268,577
Cash, cash equivalents, and restricted cash - End of Period	$ 537,002	$ 512,162