CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 10,295	$ 28,081
Other comprehensive loss:
Change in pension and postretirement obligations, net of tax of $0 and $0 in 2016	0	0
Total Other Comprehensive Income (Loss), Net of Tax	0	0
Comprehensive income (loss)	$ 10,295	$ 28,081