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	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax	$ (1,085)	$ (1,355)	$ (1,085)	$ (1,355)	$ (1,138)	$ (1,395)	$ (1,499)	$ (1,059)
Accumulated other comprehensive income (loss), beginning balance	(96,600)	(82,220)	(99,012)	(82,876)
Other comprehensive income (loss) before reclassifications:
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Gain (Loss), before Reclassification and Tax	80	224	472	(453)
Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Tax	(27)	(80)	(162)	157
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	3,408	1,866	6,816	3,732
Negative prior service cost (reclassified to salaries, wages and benefits)	(26)	(136)	(52)	(272)
Hedging gain (reclassified to interest expense)		(41)		(50)
Income Tax (Expense) or Benefit		43		46
Income Tax (Expense) or Benefit	(1,254)	(665)	(2,616)	(1,053)
Other comprehensive income (loss), net of tax	0	2	0	(4)
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax	53	144	310	(296)
Accumulated other comprehensive income (loss), ending balance	(94,392)	(80,972)	(94,392)	(80,972)
Total comprehensive income (loss)	13,783	12,032	24,413	21,797
Pension Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(95,156)	(80,049)	(97,302)	(81,191)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	3,368	1,793	6,736	3,586
Income Tax (Expense) or Benefit	(1,222)	(651)	(2,444)	(1,302)
Other comprehensive income (loss), net of tax	2,146	1,142	4,292	2,284
Accumulated other comprehensive income (loss), ending balance	(93,010)	(78,907)	(93,010)	(78,907)
Post-Retirement Plans [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	(306)	(670)	(315)	(630)
Amounts reclassified from accumulated other comprehensive income:
Actuarial costs (reclassified to salaries, wages and benefits)	40	73	80	146
Negative prior service cost (reclassified to salaries, wages and benefits)	(26)	(136)	(52)	(272)
Income Tax (Expense) or Benefit	(5)	23	(10)	46
Other comprehensive income (loss), net of tax	9	(40)	18	(80)
Accumulated other comprehensive income (loss), ending balance	(297)	(710)	(297)	(710)
Derivative [Member]
Schedule of Accumulated Other Comprehensive Income [Line Items]
Accumulated other comprehensive income (loss), beginning balance	0	(2)	0	4
Amounts reclassified from accumulated other comprehensive income:
Accumulated other comprehensive income (loss), ending balance	0	0	0	0
AOCI Attributable to Parent [Member]
Amounts reclassified from accumulated other comprehensive income:
Total comprehensive income (loss)	$ 2,208	$ 1,248	$ 4,620	$ 1,904