Accumulated Other Comprehensive Loss - Changes in Accumulated Other Comprehensive (Loss) by Component (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017
AOCI Attributable to Parent [Roll Forward]
Beginning balance	$ 3,412,152
Other comprehensive income (loss) before reclassifications, net of tax	(131,552)	$ 118,852
Amounts reclassified from accumulated other comprehensive loss, net of tax	21,867	17,235
Other comprehensive income (loss), net of income taxes	(109,685)	136,087
Ending balance	3,611,054
Pension and Other Post-Retirement Benefits [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(568,957)	(609,080)
Other comprehensive income (loss) before reclassifications, net of tax	0	0
Amounts reclassified from accumulated other comprehensive loss, net of tax	21,221	17,235
Other comprehensive income (loss), net of income taxes	21,221	17,235
Ending balance	(547,736)	(591,845)
Net Investment Hedge [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(17,388)	0
Other comprehensive income (loss) before reclassifications, net of tax	16,151	0
Amounts reclassified from accumulated other comprehensive loss, net of tax	646	0
Other comprehensive income (loss), net of income taxes	16,797	0
Ending balance	(591)	0
Foreign Currency Translation [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(266,247)	(403,941)
Other comprehensive income (loss) before reclassifications, net of tax	(147,703)	118,852
Amounts reclassified from accumulated other comprehensive loss, net of tax	0	0
Other comprehensive income (loss), net of income taxes	(147,703)	118,852
Ending balance	(413,950)	(285,089)
Total [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance	(852,592)	(1,013,021)
Ending balance	$ (962,277)	$ (876,934)