Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Statement of Cash Flows [Abstract]
Net cash provided by Operating Activities	$ 3,458	$ 311,212
Cash flows from Investing Activities:
Additions to property and equipment, including pre-delivery payments	(93,956)	(151,577)
Proceeds from the disposition of aircraft related equipment	0	4,350
Purchases of investments	(64,215)	(189,929)
Sales of investments	143,679	225,706
Other	0	(6,275)
Net cash used in investing activities	(14,492)	(117,725)
Cash flows from Financing Activities:
Long-term borrowings	283,964	0
Repayments of long-term debt and finance lease obligations	(39,129)	(77,471)
Dividend payments	(5,514)	(11,554)
Debt issuance costs	0	(33)
Repurchases of common stock	(7,510)	(30,690)
Other	(1,313)	(1,012)
Net cash provided by (used in) financing activities	230,498	(120,760)
Net increase in cash and cash equivalents	219,464	72,727
Cash, cash equivalents, and restricted cash - Beginning of Period	373,056	268,577
Cash, cash equivalents, and restricted cash - End of Period	$ 592,520	$ 341,304