QUARTERLY DATA (UNAUDITED) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 747,403	$ 755,846	$ 752,788	$ 688,941	$ 692,113	$ 729,520	$ 697,510	$ 636,083	$ 2,944,978	$ 2,755,226	$ 3,275,137
Cost of revenues	526,690	519,595	519,803	496,585	496,661	491,915	480,002	464,279	2,062,673	1,932,857	2,356,806
(Loss) income from operations	27,935	47,663	46,744	5,433	21,943	16,802	34,504	(4,087)	127,775	69,162	187,579
Other (expense) income, net	(3,305)	(432)	(833)	(1,549)	6,932	(198)	(189)	(350)	(6,119)	6,195	(1,380)
Net (loss) income	$ 84,194	$ 12,058	$ 25,880	$ (21,393)	$ (12,713)	$ (10,255)	$ 3,966	$ (20,871)	$ 100,739	$ (39,873)	$ 44,102
Basic (loss) earnings per share (in dollars per share)	$ 1.48	$ 0.21	$ 0.45	$ (0.37)	$ (0.22)	$ (0.18)	$ 0.07	$ (0.36)	$ 1.77	$ (0.69)	$ 0.76
Diluted (loss) earnings per share (in dollars per share)	$ 1.48	$ 0.21	$ 0.45	$ (0.37)	$ (0.22)	$ (0.18)	$ 0.07	$ (0.36)	$ 1.76	$ (0.69)	$ 0.76
Goodwill impairment charge						$ 34,000			$ 0	$ 34,013	$ 31,992
Gain on sale of businesses			$ 31,700			$ 16,400			30,732	16,884	0
Loss on early extinguishment of debt		$ 1,900	$ 6,000						$ 7,891	$ 0	$ 0
Tax benefit due to reduction in net deferred tax liability	$ 93,000