Consolidated Statements of Operations - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Income Statement [Abstract]
Revenues	$ 1,246,929	$ 1,200,211	$ 1,196,696
Operating expenses	918,673	890,212	868,144
Gross margin	328,256	309,999	328,552
Selling, general and administrative expenses	360,692	348,391	323,973
Restructuring and other related charges, net (see Note 17)	6,727	2,651	5,513
(Gain) loss on revaluation of contingent consideration	(202)	(1,174)	2,184
Goodwill impairment loss (see Note 1)	0	75,241	0
Operating loss	(38,961)	(115,110)	(3,118)
Interest expense, net	30,875	21,487	12,667
Write-off of deferred loan costs	0	1,244	0
Loss (gain) on convertible debt embedded derivative (see Note 10)	24,783	(818)	0
Other (income) expense, net	(410)	510	(127)
Loss from continuing operations before income taxes	(94,209)	(137,533)	(15,658)
Less: Benefit for income taxes (see Note 9)	(31,063)	(53,078)	(3,093)
Loss from continuing operations	(63,146)	(84,455)	(12,565)
Loss from discontinued operations, net of income tax	0	0	(111)
Net loss	$ (63,146)	$ (84,455)	$ (12,676)
Basic loss per common share:
Basic earnings (loss) from continuing operations per share (in USD per share)	$ (2.10)	$ (2.83)	$ (0.45)
Basic earnings (loss) from discontinued operations per share (in USD per share)	0.00	0.00	0.00
Net income (loss) per share: Basic (in USD per share)	(2.10)	(2.83)	(0.45)
Diluted loss per common share:
Diluted earnings (loss) from continuing operations per share (in USD per share)	(2.10)	(2.83)	(0.45)
Diluted earnings (loss) from discontinued operations per share (in USD per share)	0.00	0.00	0.00
Net income (loss) per share: Diluted (in USD per share)	$ (2.10)	$ (2.83)	$ (0.45)