Schedule of Amounts Recognized in Accumulated Other Comprehensive Income (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Deferred taxes	$ (12,018)	$ (12,192)	$ (11,582)
Defined Benefit Pension Plans | United States
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service cost, before tax	358	493
Deferred taxes	429	380
Total recognized in other comprehensive income, net of tax	787	873
Postretirement Benefit Plans
Schedule of Pension and Other Postretirement Benefits Recognized in Accumulated Other Comprehensive Income (Loss) [Line Items]
Prior service cost, before tax	(2,230)	(2,829)
Deferred taxes	(882)	(664)
Total recognized in other comprehensive income, net of tax	$ (3,112)	$ (3,493)