Other Intangible Assets - Schedule of Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Sep. 30, 2018	Dec. 31, 2016	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Acquired Finite-Lived Intangible Assets [Line Items]
Impairment of Intangible Assets, Finite-lived	$ 13,800	$ 100	$ 18,121	$ 0	$ 70
Gross intangible assets			77,309	78,146
Less accumulated amortization and impairment			(67,481)	(50,583)
Intangible assets, net			9,828	27,563
Customer lists
Acquired Finite-Lived Intangible Assets [Line Items]
Gross intangible assets			$ 73,792	74,615
Weighted Average Life			14 years 5 months
Non-competition agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Gross intangible assets			$ 950	964
Weighted Average Life			4 years 1 month
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Gross intangible assets			$ 2,510	2,510
Weighted Average Life			13 years 4 months
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Gross intangible assets			$ 57	$ 57
Weighted Average Life			9 years