Other Comprehensive Income (Loss) - Changes in Accumulated Other Comprehensive Income (Loss) by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
AOCI Attributable to Parent [Roll Forward]
Beginning balance, January 1			$ 3,193,728
Other comprehensive income before reclassifications, net of tax			118,852	$ 50,840
Amounts reclassified from accumulated other comprehensive loss, net of tax			17,235	14,268
Total other comprehensive income	$ 44,455	$ 16,655	136,087	65,108
Ending balance, September 30	3,378,235		3,378,235
Pension and Other Post-Retirement Benefits [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance, January 1			(609,080)	(535,634)
Other comprehensive income before reclassifications, net of tax			0	0
Amounts reclassified from accumulated other comprehensive loss, net of tax			17,235	14,268
Total other comprehensive income			17,235	14,268
Ending balance, September 30	(591,845)	(521,366)	(591,845)	(521,366)
Accumulated Foreign Currency Adjustment Attributable to Parent [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance, January 1			(403,941)	(394,984)
Other comprehensive income before reclassifications, net of tax			118,852	50,840
Amounts reclassified from accumulated other comprehensive loss, net of tax			0	0
Total other comprehensive income			118,852	50,840
Ending balance, September 30	(285,089)	(344,144)	(285,089)	(344,144)
AOCI Attributable to Parent [Member]
AOCI Attributable to Parent [Roll Forward]
Beginning balance, January 1			(1,013,021)	(930,618)
Ending balance, September 30	$ (876,934)	$ (865,510)	$ (876,934)	$ (865,510)