Accounting Policies - Accumulated Other Comprehensive Loss by Component, Net of Tax (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 2,808,868
Other comprehensive income (loss) before reclassifications			(112,827)	$ 193,028
Amounts reclassified from accumulated other comprehensive income			1,618	2,027
Other comprehensive (loss) income, net of tax	$ (190,217)	$ 147,100	(111,209)	195,053
Ending balance	2,857,280		2,857,280
Foreign currency translation
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			5,063	(321,033)
Other comprehensive income (loss) before reclassifications			(114,811)	195,079
Amounts reclassified from accumulated other comprehensive income			0	0
Other comprehensive (loss) income, net of tax			(114,811)	195,079
Ending balance	(109,748)	(125,954)	(109,748)	(125,954)
Derivative contracts
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			4,015	(2,957)
Other comprehensive income (loss) before reclassifications			(4,760)	1,978
Amounts reclassified from accumulated other comprehensive income			579	843
Other comprehensive (loss) income, net of tax			(4,181)	2,821
Ending balance	(166)	(136)	(166)	(136)
Pension and post retirement benefit plans
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(54,070)	(55,615)
Other comprehensive income (loss) before reclassifications			6,744	(4,029)
Amounts reclassified from accumulated other comprehensive income			1,039	1,184
Other comprehensive (loss) income, net of tax			7,783	(2,845)
Ending balance	(46,287)	(58,460)	(46,287)	(58,460)
AOCI Attributable to Parent
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			(44,992)	(379,605)
Other comprehensive (loss) income, net of tax				195,055
Ending balance	$ (156,201)	$ (184,550)	$ (156,201)	$ (184,550)