CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME (LOSS) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement of Comprehensive Income [Abstract]
Net loss		$ (160,843)	$ (757,744)	$ (447,710)
Other comprehensive income (loss), net of tax:
Pension liability adjustment	[1]	767	(1,154)	(2,090)
Total other comprehensive income (loss), net of tax		767	(1,154)	(2,090)
Total comprehensive loss		$ (160,076)	$ (758,898)	$ (449,800)

[1] Please refer to Note 8 – Pension Benefits for additional discussion on the pension liability adjustment.