Financial Instruments - Additional Information (Detail) (USD $)	3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended		3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended	1 Months Ended
	Jun. 30, 2012	Jun. 30, 2012	Jun. 30, 2012 Accrued liabilities	Jun. 30, 2012 Other liabilities	Jun. 30, 2012 Interest rate swap agreements	Jun. 30, 2012 Interest rate swap agreements	Apr. 30, 2012 Interest rate swap agreements Contract	Jun. 30, 2012 Natural gas swap agreements MMBtu	Jun. 30, 2012 Natural gas swap agreements MMBtu	Jun. 30, 2012 Natural gas swap agreements Minimum	Jun. 30, 2012 Natural gas swap agreements Maximum	Jun. 30, 2012 Foreign Currency Exchange Rate Risk	Jun. 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	$ 12,800,000	$ 12,800,000	$ 5,000,000	$ 7,800,000
Amount of loss reclassified to earnings from derivatives component of accumulated other comprehensive (loss) income	900,000	1,700,000
Estimated amount of loss to be reclassified to earnings from derivatives component of accumulated other comprehensive (loss) income during the next twelve months		2,600,000
Aggregate notional principal amount of outstanding interest rate swap agreements					280,700,000	280,700,000
Net payments under derivative swap agreements					1,000,000	2,000,000		500,000	1,000,000
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								390,000	390,000
Natural gas fixed prices per MMBtu										2.587	4.814
Percentage of hedged estimated twelve month exposure to fluctuations in natural gas prices								9.00%	9.00%
Foreign currency losses of net investment hedges included in accumulated other comprehensive (loss) income												$ 26,600,000	$ 16,200,000