Note Other comprehensive income (loss) (Disclosure of accumulated other comprehensive income (loss)) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Foreign Currency Translation
Beginning Balance	$ (49,936)	$ (43,034)
Other comprehensive loss before reclassifications	(1,238)	93
Net change	(1,238)	93
Ending Balance	(51,174)	(42,941)
Adjustment of pension and postretirement benefit plans
Beginning Balance	(203,836)	(205,408)
Amounts reclassified from accumulated other comprehensive income (loss) for amortization of net losses	3,673	3,285
Amounts reclassified from accumulated other comprehensive income (loss) for amortization of prior service credit	0	(529)
Net change	3,673	2,756
Ending Balance	(200,163)	(202,652)
Unrealized net holding losses on debt securities
Beginning Balance	(173,811)	(102,775)
Other comprehensive (loss) income before reclassifications	101,403	(114,404)
Net change	101,403	(114,404)
Ending Balance	(72,408)	(217,179)
Unrealized holding gains on equity securities
Beginning Balance	0	605
Reclassification to retained earnings due to cumulative effect of accounting change	0	(605)
Net change	0	(605)
Ending Balance	0	0
Unrealized net (losses) gain on cash flow hedges
Beginning Balance	(391)	(40)
Reclassification to retained earnings due to cumulative effect of accounting change	(50)	0
Other comprehensive income (loss) before reclassification	(437)	747
Amounts reclassified from other accumulated other comprehensive income (loss)	644	(773)
Net change	157	(26)
Ending Balance	(234)	(66)
Accumulated other comprehensive (loss) income	$ (323,979)	$ (462,838)	$ (427,974)