Estimated Amounts to Be Amortized from Accumulated Other Comprehensive Income into Net Periodic Benefit Costs (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	$ (95)	$ (697)	$ (1,704)
Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	(757)	(953)	(986)
Domestic Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	(812)	(1,009)	(1,038)
Forecast for 2013 | Postretirement Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	(95)
Forecast for 2013 | Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	(686)
Forecast for 2013 | Domestic Pension Benefits
Defined Benefit Plan Disclosure [Line Items]
Amortization of prior service benefit	$ (741)