Condensed Consolidated Statements of Comprehensive Income (Loss) (unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ (99,140)	$ 83,464	$ (271,396)	$ 254,041
Unrealized gain (loss) on short-term investment securities and cash and cash equivalents, net of deferred taxes of $(47), $(20), $12 and $47	(162)	(68)	41	161
Interest rate derivative loss reclassified into earnings, net of taxes of $14, $17, $53 and $63	49	57	138	157
Other comprehensive income (loss)	(113)	(11)	179	318
Comprehensive income (loss)	$ (99,253)	$ 83,453	$ (271,217)	$ 254,359