Other Intangible Assets - Schedule of Other Intangible Assets (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Dec. 31, 2018
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 77,225	$ 77,309
Less accumulated amortization	(68,451)	(67,481)
Intangible assets, net	8,774	9,828
Trade names
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 2,510	2,510
Acquired finite-lived intangible assets, weighted average useful life	13 years 3 months
Customer lists
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 73,708	73,792
Less accumulated amortization	$ (65,400)	(64,500)
Acquired finite-lived intangible assets, weighted average useful life	14 years 5 months
Noncompete agreements
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 950	950
Acquired finite-lived intangible assets, weighted average useful life	4 years 1 month
Patents
Acquired Finite-Lived Intangible Assets [Line Items]
Finite-lived intangible assets, gross	$ 57	$ 57
Acquired finite-lived intangible assets, weighted average useful life	9 years