Consolidated Statements of Comprehensive Income (Loss) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (428,700)	$ 335,255	$ 155,749
Unrealized gain (loss) on short-term investment securities and cash and cash equivalents, net of deferred taxes of $(1), $38 and $44	(20)	167	30
Interest rate derivative loss reclassified into earnings, net of taxes of $63, $76 and $75	189	239	241
Other comprehensive income (loss)	169	406	271
Comprehensive income (loss)	$ (428,531)	$ 335,661	$ 156,020