Accumulated Other Comprehensive Income (Loss) - Reclassifications of Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Total reclassifications for the period	$ (1,812)	$ (1,851)
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Attributable to Parent [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	125	0
Accumulated Defined Benefit Plans Adjustment, Net Gain (Loss) Attributable to Parent [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	(3,058)	(2,847)
Pension and Postretirement Plans
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Reclassification from AOCI before tax	(2,933)	(2,847)
Income tax expense	1,121	996
Total reclassifications for the period	$ (1,812)	$ (1,851)