Summary of Significant Accounting Policies - Changes in Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2017	Dec. 31, 2016
Changes in Accumulated Other Comprehensive Loss by Component
Beginning balance	$ 3,193,728
Other comprehensive (loss) income before reclassifications, net of tax	137,253	$ (101,700)
Amounts reclassified from accumulated other comprehensive loss, net of tax	23,176	19,297
Net current period other comprehensive income (loss)	160,429	(82,403)
Ending balance	3,412,152	3,193,728
Pension Benefits [Member]
Changes in Accumulated Other Comprehensive Loss by Component
Beginning balance	(607,468)	(534,215)
Other comprehensive (loss) income before reclassifications, net of tax	16,640	(92,758)
Amounts reclassified from accumulated other comprehensive loss, net of tax	23,385	19,505
Net current period other comprehensive income (loss)	40,025	(73,253)
Ending balance	(567,443)	(607,468)
Other Post-Retirement Benefits [Member]
Changes in Accumulated Other Comprehensive Loss by Component
Beginning balance	(1,612)	(1,419)
Other comprehensive (loss) income before reclassifications, net of tax	307	15
Amounts reclassified from accumulated other comprehensive loss, net of tax	(209)	(208)
Net current period other comprehensive income (loss)	98	(193)
Ending balance	(1,514)	(1,612)
Net Investment Hedge [Member]
Changes in Accumulated Other Comprehensive Loss by Component
Beginning balance	0	0
Other comprehensive (loss) income before reclassifications, net of tax	(17,388)	0
Amounts reclassified from accumulated other comprehensive loss, net of tax	0	0
Net current period other comprehensive income (loss)	(17,388)	0
Ending balance	(17,388)	0
Foreign Currency Translation [Member]
Changes in Accumulated Other Comprehensive Loss by Component
Beginning balance	(403,941)	(394,984)
Other comprehensive (loss) income before reclassifications, net of tax	137,694	(8,957)
Amounts reclassified from accumulated other comprehensive loss, net of tax	0	0
Net current period other comprehensive income (loss)	137,694	(8,957)
Ending balance	(266,247)	(403,941)
Accumulated Other Comprehensive Loss [Member]
Changes in Accumulated Other Comprehensive Loss by Component
Beginning balance	(1,013,021)	(930,618)
Ending balance	$ (852,592)	$ (1,013,021)

Amount after tax, before reclassification adjustments, of other comprehensive income (loss), attributable to parent.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
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-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 55
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