Unaudited Condensed Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Income Statement [Abstract]
Revenues	$ 315,829	$ 343,889	$ 585,428	$ 646,274
Operating expenses	221,232	246,707	424,884	473,558
Gross margin	94,597	97,182	160,544	172,716
Selling, general and administrative expenses	81,593	93,174	163,860	182,833
Restructuring and other related charges, net	0	2,411	208	2,411
Gain on revaluation of contingent consideration	0	(202)	0	(202)
Operating income (loss)	13,004	1,799	(3,524)	(12,326)
Interest expense, net	7,586	7,631	15,011	15,228
Loss on convertible debt embedded derivative (see Note 8)	0	29,330	0	24,783
Other expense, net	313	285	255	332
Loss before income taxes	5,105	(35,447)	(18,790)	(52,669)
Less: Provision (benefit) for income taxes	(997)	(4,106)	(664)	(9,064)
Net income (loss)	$ 6,102	$ (31,341)	$ (18,126)	$ (43,605)
Basic loss per share	$ 0.20	$ (1.04)	$ (0.60)	$ (1.45)
Diluted loss per share	$ 0.20	$ (1.04)	$ (0.60)	$ (1.45)