Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		$ (126,261)
Other comprehensive income (loss)		(13,877)	$ (45,140)	$ 40,469
Ending balance		(140,138)	(126,261)
Accumulated Translation Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance		(20,676)	(14,219)
Other comprehensive income (loss), before reclassifications		(1,949)	(3,833)
Reclassification from AOCI to net income		0	(2,624)
Other comprehensive income (loss)		(1,949)	(6,457)
Ending balance		(22,625)	(20,676)	(14,219)
Accumulated Defined Benefit Plans Adjustment [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[1]	(105,264)	(66,317)
Other comprehensive income (loss)	[1]	(12,191)	(38,947)
Ending balance	[1]	(117,455)	(105,264)	(66,317)
Accumulated Defined Benefit Plan & SERP, Net Prior Service Cost [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI to net income	[1]	36	61
Reclassification from AOCI, tax		(21)	(37)
Accumulated Defined Benefit Plan & SERP, Amortization of Net Loss [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI to net income	[1]	6,315	2,614
Reclassification from AOCI, tax		(3,823)	(1,583)
Accumulated Defined Benefit Plan & SERP, Change in Net Gain [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Reclassification from AOCI to net income	[1]	(18,542)	(41,622)
Reclassification from AOCI, tax		11,226	25,203
Accumulated Net Gain (Loss) from Designated or Qualifying Cash Flow Hedges [Member]
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	[2]	(321)	(585)
Other comprehensive income (loss), before reclassifications	[2]	(108)	(268)
Reclassification from AOCI to net income	[2]	371	532
Other comprehensive income (loss)	[2]	263	264
Ending balance	[2]	(58)	(321)	$ (585)
OCI before reclassifications to net income, tax		66	162
Reclassification from AOCI, tax		$ (224)	$ (323)

[1] These accumulated other comprehensive income components are included in the computation of net periodic pension cost (see Note 14, Pension Plans for additional information)

[2] See Note 6, Derivative Financial Instruments, for additional information regarding our derivative instruments.