Shareholders' equity - change in accumulated other comprehensive income (loss), net of tax (Detail) - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2018	Dec. 31, 2017
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	$ 2,430,531	$ 2,137,517
Ending Balance	2,539,978	2,430,531
Cash Flow Hedges
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	340	(2,424)
Other comprehensive income (loss) before reclassifications	2,574	2,775
Amounts reclassified from accumulated other comprehensive income (loss)	(2,107)	(11)
Net current-year other comprehensive income (loss)	467	2,764
Ending Balance	807	340
Pension and Other Postretirement Benefit Plans
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(138,808)	(136,596)
Other comprehensive income (loss) before reclassifications	1,605	(6,725)
Amounts reclassified from accumulated other comprehensive income (loss)	5,823	4,513
Net current-year other comprehensive income (loss)	7,428	(2,212)
Ending Balance	(131,380)	(138,808)
Foreign Currency Translation Adjustment
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(126,623)	(299,697)
Other comprehensive income (loss) before reclassifications	(83,889)	173,074
Amounts reclassified from accumulated other comprehensive income (loss)	0	0
Net current-year other comprehensive income (loss)	(83,889)	173,074
Ending Balance	(210,512)	(126,623)
Accumulated Other Comprehensive Income (loss)
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Beginning Balance	(265,091)	(438,717)
Other comprehensive income (loss) before reclassifications	(79,710)	169,124
Amounts reclassified from accumulated other comprehensive income (loss)	3,716	4,502
Net current-year other comprehensive income (loss)	(75,994)	173,626
Ending Balance	$ (341,085)	$ (265,091)

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

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Amount of increase (decrease) in other comprehensive income, after tax, from changes classified as other.

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Amount after tax of reclassification adjustments of other comprehensive income (loss).

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Amount of stockholders' equity (deficit), net of receivables from officers, directors, owners, and affiliates of the entity, attributable to both the parent and noncontrolling interests. Amount excludes temporary equity. Alternate caption for the concept is permanent equity.

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