Goodwill and Other Intangible Assets - Intangible Assets (Details) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Schedule of Finite-Lived and Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 200,822	$ 84,246
Accumulated Amortization	(70,355)	(61,525)
Total indefinite-lived intangible assets	30	32
Total intangible assets	$ 200,852	$ 84,278
Finite-Lived Intangible Assets, Remaining Amortization Period	16 years 170 days	3 years 36 days
Licensing Agreements
Schedule of Finite-Lived and Indefinite-lived Intangible Assets [Line Items]
Total indefinite-lived intangible assets	$ 30	$ 32
Customer relationships
Schedule of Finite-Lived and Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	42,606	45,209
Accumulated Amortization	(34,587)	(33,997)
Trade name
Schedule of Finite-Lived and Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	1,468	0
Accumulated Amortization	(971)	0
Contracts / agreements
Schedule of Finite-Lived and Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	153,588	38,362
Accumulated Amortization	(33,983)	(26,853)
Favorable lease contract
Schedule of Finite-Lived and Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	2,485	0
Accumulated Amortization	(139)	0
Noncompete agreements
Schedule of Finite-Lived and Indefinite-lived Intangible Assets [Line Items]
Gross Carrying Amount	675	675
Accumulated Amortization	$ (675)	$ (675)