Accumulated Other Comprehensive Income (Loss) - Reclassifications of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016	Jun. 30, 2015
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	$ 71	$ (576)	$ (1,741)	$ (2,427)
Prior service cost
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	113	0	238	0
Actuarial losses
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	0	(885)	(3,058)	(3,732)
Pension and Postretirement Plans
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	113	(885)	(2,820)	(3,732)
Income tax expense	(42)	309	1,079	1,305
Total reclassifications for the period	$ 71	$ (576)	$ (1,741)	$ (2,427)