Geographic Information on Sales to External Customers (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2013	Sep. 30, 2013	Jun. 30, 2013	Mar. 31, 2013	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Segment Reporting, Revenue Reconciling Item [Line Items]
Sales to external customers	$ 291,429	$ 264,884	$ 285,859	$ 269,886	$ 282,341	$ 270,480	$ 279,367	$ 278,255	$ 1,112,058	$ 1,110,443	$ 1,112,814
UNITED STATES
Segment Reporting, Revenue Reconciling Item [Line Items]
Sales to external customers									528,178	527,550	538,257
GERMANY
Segment Reporting, Revenue Reconciling Item [Line Items]
Sales to external customers									71,139	74,557	75,536
Other Country
Segment Reporting, Revenue Reconciling Item [Line Items]
Sales to external customers									$ 512,741	$ 508,336	$ 499,021