CONSOLIDATED STATEMENTS OF OPERATIONS - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Income Statement [Abstract]
REVENUES	$ 1,595,227	$ 728,974	$ 1,263,840
COSTS AND EXPENSES:
Cost of revenues (exclusive of items shown separately below)	1,050,809	607,888	986,144
Selling, general and administrative expenses	159,194	150,690	156,579
Depreciation and amortization	163,537	217,258	270,977
(Gain) loss on disposition of assets, net	(4,530)	(7,920)	6,417
Operating profit (loss)	226,217	(238,942)	(156,277)
Interest expense	(426)	(681)	(2,032)
Interest income	1,494	467	83
Other (expense) income, net	5,531	(204)	5,185
Income (loss) before income taxes	232,816	(239,360)	(153,041)
Income tax provision (benefit)	70,305	(98,114)	(53,480)
Net income (loss)	$ 162,511	$ (141,246)	$ (99,561)
EARNINGS (LOSS) PER SHARE
Basic (in dollars per share)	$ 0.75	$ (0.66)	$ (0.47)
Diluted (in dollars per share)	0.75	(0.66)	(0.47)
Dividends paid per share (in dollars per share)	$ 0.200	$ 0.050	$ 0.155