Goodwill and Intangible Assets (Details Textual) - USD ($) $ in Thousands	3 Months Ended	6 Months Ended
Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Goodwill And Intangible Assets Disclosure [Abstract]
Goodwill associated with the Company's purchase and other past acquisitions	$ 38,201		$ 38,201		$ 38,201
Aggregate amortization expense	$ 355	$ 364	$ 709	$ 729

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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