CONSOLIDATED STATEMENTS OF OPERATIONS (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Income Statement [Abstract]
Revenues	$ 334,656	$ 436,334
Cost of revenues (exclusive of items shown below)	252,395	295,605
Selling, general and administrative expenses	45,421	43,814
Depreciation and amortization	42,505	37,480
Gain on disposition of assets, net	(3,504)	(1,363)
Operating (loss) income	(2,161)	60,798
Interest expense	(89)	(105)
Interest income	800	402
Other income, net	445	5,395
(Loss) income before income taxes	(1,005)	66,490
Income tax (benefit) provision	(266)	14,360
Net (loss) income	$ (739)	$ 52,130
Earnings per share
Basic	$ 0.00	$ 0.24
Diluted	0.00	0.24
Dividends per share	$ 0.10	$ 0.10