Note Other comprehensive income (loss) (Disclosure of accumulated other comprehensive income (loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Foreign Currency Translation
Beginning Balance	$ (43,034)	$ (39,956)
Other comprehensive loss before reclassifications	93	139
Net change	93	139
Ending Balance	(42,941)	(39,817)
Adjustment of pension and postretirement benefit plans
Beginning Balance	(205,408)	(211,610)
Amounts reclassified from accumulated other comprehensive income (loss) for amortization of net losses	3,285	3,421
Amounts reclassified from accumulated other comprehensive income (loss) for amortization of prior service credit	(529)	(580)
Net change	2,756	2,841
Ending Balance	(202,652)	(208,769)
Unrealized net holding losses on debt securities
Beginning Balance	(102,775)	(69,003)
Other comprehensive loss	(114,404)	(2,704)
Net change	(114,404)	(2,704)
Ending Balance	(217,179)	(71,707)
Unrealized holding gains on equity securities
Beginning Balance	605	685
Reclassification to retained earnings due to cumulative effect adjustment	(605)	0
Other comprehensive income before reclassifications	0	95
Amounts reclassified from accumulated other comprehensive income	0	(130)
Net change	(605)	(35)
Ending Balance	0	650
Unrealized net (losses) gain on cash flow hedges
Beginning Balance	(40)	(402)
Other comprehensive (loss) income before reclassifications	747	(389)
Amounts reclassified from other accumulated other comprehensive (loss) income	(773)	522
Net change	(26)	133
Ending Balance	(66)	(269)
Accumulated other comprehensive (loss) income	$ (462,838)	$ (319,912)	$ (350,652)