CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 70,589	$ 224,785	$ 32,662
Other comprehensive income (loss):
Change in pension and postretirement obligations, net of tax	(141)	82	(73)
Total other comprehensive income (loss), net of tax	(141)	82	(73)
Comprehensive income	$ 70,448	$ 224,867	$ 32,589