Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Cash Flows [Abstract]
Net cash provided by Operating Activities	$ 46,887	$ 150,680
Cash flows from Investing Activities:
Additions to property and equipment, including pre-delivery payments	(46,845)	(74,261)
Proceeds from the disposition of aircraft related equipment	0	2,780
Purchases of investments	(48,133)	(71,454)
Sales of investments	80,218	137,286
Other	0	(6,275)
Net cash used in investing activities	(14,760)	(11,924)
Cash flows from Financing Activities:
Long-term borrowings	235,000	0
Repayments of long-term debt and finance lease obligations	(25,320)	(24,354)
Dividend payments	(5,514)	(5,811)
Repurchases of common stock	(7,510)	(11,086)
Other	(1,230)	(982)
Net cash provided by (used in) financing activities	195,426	(42,233)
Net increase in cash and cash equivalents	227,553	96,523
Cash, cash equivalents, and restricted cash - Beginning of Period	373,056	268,577
Cash, cash equivalents, and restricted cash - End of Period	$ 600,609	$ 365,100