Employee Benefit Plans - Other Plan Changes Recognized in Other Comprehensive (Income) Loss (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Defined Benefit Plan [Abstract]
Net actuarial (gain) loss	$ 234	$ (166)	$ (538)
Amortization of prior service cost	0	0	0
Total recognized in other comprehensive (income) loss	234	(166)	(538)
Total Recognized in Net Periodic Benefit Cost and Other Comprehensive (Income) Loss	$ 471	$ 261	$ 264