Condensed Consolidated Statements of Comprehensive (Loss)/Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Income Statement [Abstract]
Net (loss)/income	$ (15,868)	$ 25,125
Defined benefit pension and other postretirement benefit plans:
Net change in unrecognized prior service costs	(180)	(18)
Net change in unrecognized actuarial losses	81	76
Other comprehensive (loss)/income	(99)	58
Comprehensive (loss)/income	$ (15,967)	$ 25,183