Disclosure of accumulated other comprehensive income (loss) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended						9 Months Ended
	Sep. 30, 2014		Mar. 31, 2014		Sep. 30, 2013		Sep. 30, 2014		Sep. 30, 2013		Dec. 31, 2013
Foreign Currency Abstract
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax, Beginning Balance	$ (31,099)	[1]	$ (36,099)	[1]	$ (33,206)	[1]	$ (36,099)	[1]	$ (31,277)	[1]
Other Comprehensive Income Foreign Currency Transaction And Translation Gain Loss Arising During Period Net Of Tax	98	[1]			(2,013)	[1]	(2,620)	[1]	(3,942)	[1]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Reclassification Adjustment Realized upon Sale or Liquidation, before Tax	0	[1]	7,700		0	[1]	7,718	[1]	0	[1]
Other Comprehensive Income (Loss), Foreign Currency Transaction and Translation Adjustment, Net of Tax, Portion Attributable to Parent, Total	98	[1]			(2,013)	[1]	5,098	[1]	(3,942)	[1]
Accumulated Other Comprehensive Income (Loss), Foreign Currency Translation Adjustment, Net of Tax, Ending Balance	(31,001)	[1]			(35,219)	[1]	(31,001)	[1]	(35,219)	[1]
Defined Benefit Pension Plans And Defined Benefit Postretirement Plans Disclosure Abstract
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax, Beginning Balance	(102,867)	[1]	(104,302)	[1]	(218,321)	[1]	(104,302)	[1]	(225,846)	[1]
Other Comprehensive Income Loss Amortization Adjustment From A O C I Pension And Other Postretirement Benefit Plans For Net Prior Service Cost Credit Net Of Tax	(580)	[1]			0	[1]	(1,738)	[1]	0	[1]
Other Comprehensive IncomeLoss Reclassification AdjustmentFrom A O C I Pension And Other Postretirement Benefit Plans For Net Gain Loss Net Of Tax	1,298	[1]			3,762	[1]	3,891	[1]	11,287	[1]
Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Adjustment, Net of Tax, Portion Attributable to Parent, Total	718	[1]			3,762	[1]	2,153	[1]	11,287	[1]
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans, Net of Tax, Ending Balance	(102,149)	[1]			(214,559)	[1]	(102,149)	[1]	(214,559)	[1]
Unrealized Gain Loss On Investments Abstract
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Beginning Balance	4,071	[1]	(48,344)	[1]	23,990	[1]	(48,344)	[1]	154,568	[1]
Other Comprehensive Income Loss Available For Sale Securities Adjustment Before Reclassification Adjustments	(19,095)	[1]			(29,503)	[1]	33,320	[1]	(160,081)	[1]
Other Comprehensive Income Loss Reclassification Adjustment From A O C I For Sale Of Securities Net Of Tax	(1,763)	[1]			0	[1]	(1,763)	[1]	0	[1]
Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Total	(20,858)	[1]			(29,503)	[1]	31,557	[1]	(160,081)	[1]
Accumulated Other Comprehensive Income (Loss), Available-for-sale Securities Adjustment, Net of Tax, Ending Balance	(16,787)	[1]			(5,513)	[1]	(16,787)	[1]	(5,513)	[1]
Unrealized net gain (losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax, Beginning Balance	(396)	[1]	0	[1]	1,498	[1]	0	[1]	(313)	[1]
Other Comprehensive Income Unrealized Gain Loss On Derivatives Arising During Period	(417)	[1]			(2,325)	[1]	(3,024)	[1]	1,436	[1]
Other Comprehensive Income Loss Reclassification Adjustment From A O C I On Derivatives Net Of Tax	683	[1]			(888)	[1]	2,894	[1]	(2,838)	[1]
Other Comprehensive Income (Loss), Derivatives Qualifying as Hedges, Net of Tax, Portion Attributable to Parent, Total	266	[1]			(3,213)	[1]	(130)	[1]	(1,402)	[1]
Accumulated Other Comprehensive Income (Loss), Cumulative Changes in Net Gain (Loss) from Cash Flow Hedges, Effect Net of Tax, Ending Balance	(130)	[1]			(1,715)	[1]	(130)	[1]	(1,715)	[1]
Accumulated other comprehensive income (loss)	$ (150,067)				$ (257,006)	[1]	$ (150,067)		$ (257,006)	[1]	$ (188,745)

[1] All amounts presented are net of tax.