Stock Based Compensation - Recorded in Corporate Expense, Net, on Consolidated Statements of Operations (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Stock compensation expense before tax benefit	$ 76	$ 131	$ 150
Income tax benefit	(22)	(50)	(58)
Stock compensation expense after tax benefit	$ 54	$ 81	$ 92