Accumulated Other Comprehensive Income (Loss) - Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Amortization of pension and postretirement benefits items:
Prior service benefit/cost	$ (25)	$ (6)
Amortization of actuarial loss	9	88
Total before tax	(16)	82
Income tax	4	(21)
Amount reclassified out of accumulated other comprehensive income (loss)	$ (12)	$ 61