CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
CONSOLIDATED STATEMENTS OF COMPREHENSIVE INCOME
NET INCOME	$ 14,788	$ 12,940	$ 23,158	$ 17,068
Pension and other postretirement benefit plans:
Net actuarial gain (loss), net of tax of: (2017 - Three-month period $1,011, Nine-month period $2,010; 2016 -Three-month period $822, Nine-month period $2,637)	(1,589)	1,294	(3,158)	(4,141)
Pension settlement expense, net of tax of: (2017 - Three-month period $366, Nine-month period $1,417; 2016 - Three-month period $313, Nine-month period $882)	577	490	2,227	1,385
Amortization of unrecognized net periodic benefit costs, net of tax of: (2017 - Three-month period $331, Nine-month period $1,084; 2016 - Three-month period $496, Nine-month period $1,410)
Net actuarial loss	547	807	1,788	2,301
Prior service credit	(29)	(29)	(87)	(87)
Interest rate swap and foreign currency translation:
Change in unrealized income (loss) on interest rate swap, net of tax of: (2017 - Three-month period $16, Nine-month period $156; 2016 - Three-month period $168, Nine-month period $278)	25	262	241	(430)
Change in foreign currency translation, net of tax of: (2017 - Three-month period $190, Nine month-period $132; 2016 - Three-month period $127, Nine-month period $158)	294	(420)	205	29
OTHER COMPREHENSIVE INCOME (LOSS), net of tax	(175)	2,404	1,216	(943)
TOTAL COMPREHENSIVE INCOME	$ 14,613	$ 15,344	$ 24,374	$ 16,125