CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement of Other Comprehensive Income [Abstract]
Net loss	$ (238,301)	$ (113,661)	$ (278,109)	$ (106,846)
Employee benefit plans:
Amortization of and adjustments to employee benefit costs	(7,121)	1,187	(11,131)	1,426
Income tax expense	0	(310)	0	(372)
Total other comprehensive (loss) income, net of tax	(7,121)	877	(11,131)	1,054
Total comprehensive loss	$ (245,422)	$ (112,784)	$ (289,240)	$ (105,792)