Accumulated Other Comprehensive Income (Loss) - Reclassifications Out of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018
Amortization of pension and postretirement benefits items:
Actuarial loss	$ (40)	$ 274
Settlement expense	526	8,168
Total before tax	486	(7,686)
Income tax	(137)	1,914
Amount reclassified out of accumulated other comprehensive income	(349)	(5,772)
Prior service benefit/cost		(756)
Total before tax	(486)	7,686
Income tax	137	(1,914)
Amount reclassified out of accumulated other comprehensive income (loss)	$ 349	$ 5,772