Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended		3 Months Ended	9 Months Ended			3 Months Ended	9 Months Ended	1 Months Ended
	Sep. 30, 2012	Sep. 30, 2012	Sep. 30, 2012 Accrued liabilities	Sep. 30, 2012 Other liabilities	Sep. 30, 2012 Interest rate swap agreements	Sep. 30, 2012 Interest rate swap agreements	Apr. 30, 2012 Interest rate swap agreements Contract	Sep. 30, 2012 Natural gas swap agreements MMBTU	Sep. 30, 2012 Natural gas swap agreements MMBTU	Sep. 30, 2012 Natural gas swap agreements Minimum	Sep. 30, 2012 Natural gas swap agreements Maximum	Sep. 30, 2012 Foreign Currency Exchange Rate Risk	Sep. 30, 2012 Foreign Currency Exchange Rate Risk	Apr. 30, 2012 Interest Rate Swap Contract One	Apr. 30, 2012 Interest Rate Swap Contract Two	Apr. 30, 2012 Interest Rate Swap Contract Three
Derivative [Line Items]
Fair value of total outstanding swap agreements	$ 13,800,000	$ 13,800,000	$ 5,300,000	$ 8,500,000
Amount of loss reclassified to earnings from derivatives component of accumulated other comprehensive (loss) income	800,000	2,500,000
Estimated amount of loss to be reclassified to earnings from derivatives component of accumulated other comprehensive (loss) income during the next twelve months, net of income taxes		2,900,000
Aggregate notional principal amount of outstanding interest rate swap agreements					285,600,000	285,600,000
Net payments under derivative swap agreements					1,200,000	3,200,000		200,000	1,200,000
Number of interest rate swap agreements							3
Notional principal amount for each interest rate swap agreement							50,000,000
Interest rate swap agreement fixed interest rate														0.75%	1.38%	1.64%
Interest rate swap agreement maturity period														2015-06	2017-06	2017-06
Interest rate swap agreement beginning period															2013-06	2014-06
Aggregate notional principal amount of natural gas swap agreements								546,000	546,000
Natural gas fixed prices per MMBtu										3.029	4.814
Percentage of hedged estimated twelve month exposure to fluctuations in natural gas prices								13.00%	13.00%
Foreign currency losses of net investment hedges included in accumulated other comprehensive (loss) income												$ (15,100,000)	$ 1,100,000