The aggregate expense charged against earnings to allocate the cost of intangible assets (nonphysical assets not used in production) in a systematic and rational manner to the periods expected to benefit from such assets. As a noncash expense, this element is added back to net income when calculating cash provided by or used in operations using the indirect method.

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Intangible Assets (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
Intangible Assets (Details) - USD ($) $ in Thousands	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Finite-Lived Intangible Assets [Line Items]
Intangible assets, net of accumulated amortization of $8,729 and $8,218, respectively	$ 78,935		$ 78,935		$ 79,446
Finite-Lived Intangible Assets, Gross	87,664		87,664		87,664
Amortization of Intangible Assets	254	$ 272	$ 509	$ 546
Noncompete Agreements [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			18 years
Finite-Lived Intangible Assets, Gross	4,918		$ 4,918		1,125
Contract-Based Intangible Assets [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			9 years
Finite-Lived Intangible Assets, Gross	$ 0		$ 0		$ 0
Minimum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			7 years
Maximum [Member]
Finite-Lived Intangible Assets [Line Items]
Finite-Lived Intangible Asset, Useful Life			15 years