Business Segments (Details 2) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended
	Dec. 31, 2012	Sep. 30, 2012	Jun. 30, 2012	Mar. 31, 2012	Dec. 31, 2011	Sep. 30, 2011	Jun. 30, 2011	Mar. 31, 2011	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenues
Total revenues	$ 204,835	$ 187,203	$ 189,629	$ 186,042	$ 215,113	$ 202,967	$ 202,838	$ 190,718	$ 767,709	$ 811,636	$ 820,720
Property, plant and equipment
Total long-lived assets	61,971				68,892				61,971	68,892
United States
Revenues
Total revenues									678,736	720,747	728,205
Property, plant and equipment
Total long-lived assets	55,467				62,538				55,467	62,538
Foreign countries
Revenues
Total revenues									88,973	90,889	92,515
Property, plant and equipment
Total long-lived assets	$ 6,504				$ 6,354				$ 6,504	$ 6,354