CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE 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 Other Comprehensive Income [Abstract]
Net loss	$ (68,637)	$ (68,532)	$ (346,746)	$ (175,378)
Employee benefit plans:
Amortization of and adjustments to employee benefit costs	1,133	(86)	(9,998)	1,340
Income tax expense	0	22	0	(350)
Total other comprehensive income (loss), net of tax	1,133	(64)	(9,998)	990
Total comprehensive loss	$ (67,504)	$ (68,596)	$ (356,744)	$ (174,388)