QUARTERLY DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 692,113	$ 729,520	$ 697,510	$ 636,083	$ 713,044	$ 893,366	$ 936,228	$ 732,499	$ 2,755,226	$ 3,275,137	$ 3,401,636
Cost of revenues	496,661	491,915	480,002	464,279	522,965	634,646	652,688	546,507	1,932,857	2,356,806	2,441,796
(Loss) income from operations	21,943	16,802	34,504	(4,087)	25,549	93,970	60,758	7,302	69,162	187,579	111,810
Other income (expense), net	6,932	(198)	(189)	(350)	(990)	(139)	(660)	409	6,195	(1,380)	4,380
Net (loss) income	$ (12,713)	$ (10,255)	$ 3,966	$ (20,871)	$ 568	$ 40,228	$ 10,395	$ (7,089)	$ (39,873)	$ 44,102	$ (28,328)
Basic (loss) earnings per share (in dollars per share)	$ (0.22)	$ (0.18)	$ 0.07	$ (0.36)	$ 0.01	$ 0.69	$ 0.18	$ (0.12)	$ (0.69)	$ 0.76	$ (0.47)
Diluted (loss) earnings per share (in dollars per share)	$ (0.22)	$ (0.18)	$ 0.07	$ (0.36)	$ 0.01	$ 0.69	$ 0.18	$ (0.12)	$ (0.69)	$ 0.76	$ (0.47)
Goodwill impairment charge		$ 34,000					$ 32,000		$ 34,013	$ 31,992	$ 123,414
Gain on sale of business		$ 16,400							$ 16,884	$ 0	$ 0