CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) (UNAUDITED) (in thousands) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Statement of Comprehensive Income [Abstract]
Net income (loss)	$ 17,197	$ (119,907)	$ 334,598	$ (45,473)
Other comprehensive income (loss), net of tax:
Pension liability adjustment	198	124	458	(443)
Total other comprehensive income (loss), net of tax	198	124	458	(443)
Total comprehensive income (loss)	$ 17,395	$ (119,783)	$ 335,056	$ (45,916)