Restructuring activities (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended			9 Months Ended		12 Months Ended	3 Months Ended		9 Months Ended		12 Months Ended	9 Months Ended
	Sep. 30, 2012	Apr. 01, 2012 Workforce Reduction	Jan. 01, 2012 Workforce Reduction	Sep. 30, 2012 Workforce Reduction	Sep. 30, 2012 Workforce Reduction 2011 Restructuring Plan	Jan. 01, 2012 Workforce Reduction 2011 Restructuring Plan	Apr. 01, 2012 Fixed Asset Impairment	Jan. 01, 2012 Fixed Asset Impairment	Sep. 30, 2012 Fixed Asset Impairment	Sep. 30, 2012 Fixed Asset Impairment 2011 Restructuring Plan	Jan. 01, 2012 Fixed Asset Impairment 2011 Restructuring Plan	Sep. 30, 2012 Other Related Exit Costs
Restructuring Cost and Reserve [Line Items]
Restructuring Charge	$ 800			$ 6,126		$ 4,979			$ 9,364		$ 776	$ 1,596
Costs Incurred		5,400	5,000	4,351	2,683	867	9,300	800	9,364	0	776	902
Restructuring Reserve				$ 1,775	$ 1,429				$ 0	$ 0		$ 694