Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ (131,327)	$ (69,140)	$ 61,634
Other comprehensive income before reclassifications	(67,320)	(66,440)	(164,722)
Tax effect	9,486	(3,670)	17,359
Other comprehensive income before reclassifications, net of tax	(57,834)	(70,110)	(147,363)
Amounts reclassified out of AOCI	91,014	12,189	25,526
Tax effect	3,495	(4,266)	(8,937)
Amounts reclassified out of AOCI, net of tax	94,509	7,923	16,589
Other comprehensive income (loss)	36,675	(62,187)	(130,774)
Ending Balance	(94,652)	(131,327)	(69,140)
Pension and Other Post-Retirement Actuarial Items [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(136,422)	(155,760)	(129,918)
Other comprehensive income before reclassifications	(32,398)	15,169	(60,602)
Tax effect	9,815	(4,196)	18,117
Other comprehensive income before reclassifications, net of tax	(22,583)	10,973	(42,485)
Amounts reclassified out of AOCI	91,014	12,869	25,604
Tax effect	3,495	(4,504)	(8,961)
Amounts reclassified out of AOCI, net of tax	94,509	8,365	16,643
Other comprehensive income (loss)	71,926	19,338	(25,842)
Ending Balance	(64,496)	(136,422)	(155,760)
Currency Translation Adjustment [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	4,597	84,703	190,998
Other comprehensive income before reclassifications	(35,863)	(80,106)	(106,295)
Tax effect	0	0	0
Other comprehensive income before reclassifications, net of tax	(35,863)	(80,106)	(106,295)
Amounts reclassified out of AOCI	0	0	0
Tax effect	0	0	0
Amounts reclassified out of AOCI, net of tax	0	0	0
Other comprehensive income (loss)	(35,863)	(80,106)	(106,295)
Ending Balance	(31,266)	4,597	84,703
Unrealized Gain (Loss) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	498	1,917	554
Other comprehensive income before reclassifications	941	(1,503)	2,175
Tax effect	(329)	526	(758)
Other comprehensive income before reclassifications, net of tax	612	(977)	1,417
Amounts reclassified out of AOCI	0	(680)	(78)
Tax effect	0	238	24
Amounts reclassified out of AOCI, net of tax	0	(442)	(54)
Other comprehensive income (loss)	612	(1,419)	1,363
Ending Balance	$ 1,110	$ 498	$ 1,917