Quarterly Financial Data (Unaudited) (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Quarterly Financial Information Disclosure [Abstract]
Revenues	$ 294,195	$ 270,850	$ 281,967	$ 274,539	$ 305,367	$ 288,523	$ 280,066	$ 264,405	$ 1,121,551	$ 1,138,361	$ 1,094,402
Gross Profit	60,118	64,042	64,871	66,067	68,787	71,921	70,046	64,704	255,098	275,458	262,564
(Loss) income from operations	(27,869)	(43,212)	2,355	1,241	3,402	11,585	9,926	9,225	$ (67,485)	$ 34,138	$ 19,022
Net Income (Loss) Attributable to Parent	$ (29,251)	$ (44,937)	$ (299)	$ (1,684)	$ (738)	$ 7,116	$ 4,374	$ 5,678
Basic earnings (loss) per share (in USD per share)	$ (0.56)	$ (0.87)	$ (0.01)	$ (0.03)	$ (0.01)	$ 0.13	$ 0.08	$ 0.11	$ (1.46)	$ 0.31	$ 0.07
Diluted earnings (loss) per share (in USD per share)	$ (0.56)	$ (0.87)	$ (0.01)	$ (0.03)	$ (0.01)	$ 0.13	$ 0.08	$ 0.10	$ (1.46)	$ 0.30	$ 0.07