Accumulated Other Comprehensive Loss - Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016
Amortization of defined benefit pension items:
Prior service benefit/cost	$ (19)	$ (19)
Settlement expense		740
Amortization of actuarial loss	382	466
Total before tax	363	1,187
Income tax benefit	(129)	(431)
Amount reclassified out of accumulated other comprehensive loss	$ 234	$ 756