CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE (LOSS) INCOME (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Statement of Other Comprehensive Income [Abstract]
Net (loss) income	$ (68,532)	$ 11,894	$ (175,378)	$ 142,623
Employee benefit plans:
Amortization of and adjustments to employee benefit costs	(86)	39	1,340	(11)
Income tax expense	22	0	(350)	0
Total other comprehensive (loss) income, net of tax	(64)	39	990	(11)
Total comprehensive (loss) income	$ (68,596)	$ 11,933	$ (174,388)	$ 142,612