Summary of Significant Accounting Policies - Schedule of Changes to Obsolete Inventories Reserve (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Obsolete Inventory Reserve
Balance at beginning of year	$ 3,639	$ 3,836	$ 3,314
Net additions charged to earnings	1,295	1,017	2,530
Disposals	(1,053)	(1,214)	(2,008)
Balance at end of year	$ 3,881	$ 3,639	$ 3,836