CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
NET INCOME	$ 15,777	$ 10,231	$ 8,370	$ 4,128
Pension and other postretirement benefit plans:
Net actuarial loss, net of tax of: (2017 – Three-month period $64, Six-month period $999; 2016 – Three-month period $1,229, Six-month period $3,459)	(98)	(1,931)	(1,569)	(5,435)
Pension settlement expense, net of tax of: (2017 – Three-month period $290, Six-month period $1,051; 2016 – Three-month period $219, Six-month period $569)	454	345	1,650	895
Amortization of unrecognized net periodic benefit costs, net of tax of: (2017 – Three-month period $352, Six-month period $753; 2016 – Three-month period $477, Six-month period $914)
Net actuarial loss	581	780	1,241	1,494
Prior service credit	(29)	(29)	(58)	(58)
Interest rate swap and foreign currency translation:
Change in unrealized income (loss) on interest rate swap, net of tax of: (2017 – Three-month period $52, Six-month period $140; 2016 – Three-month period $93, Six-month period $446)	81	(146)	216	(692)
Change in foreign currency translation, net of tax of: (2017 – Three-month period $134, Six month-period $58; 2016 – Three-month period $86, Six-month period $285)	(208)	(135)	(89)	449
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	781	(1,116)	1,391	(3,347)
TOTAL COMPREHENSIVE LOSS	$ 16,558	$ 9,115	$ 9,761	$ 781