Foreign Operations and Sales (Details) (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
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Gross sales	$ 103,011	$ 77,992	$ 61,628	$ 74,581	[1]	$ 70,389	[2]	$ 59,841	$ 77,142	$ 70,559	$ 317,212	$ 277,931	$ 254,475
Long-Lived Assets	214,647					193,218					214,647	193,218	180,620
Export sales, included in domestic gross sales											86,850	32,872	31,605
Major customer (in hundredths)											18.30%
Domestic [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Gross sales											153,202	109,729	83,407
Long-Lived Assets	59,496					44,085					59,496	44,085	34,885
Foreign [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Gross sales											164,010	168,202	171,068
Long-Lived Assets	155,151					149,133					155,151	149,133	145,735
Europe [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Gross sales											210,463	150,678	156,814
North America [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Gross sales											86,974	105,439	75,979
Asia [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Gross sales											13,800	12,827	10,448
Other [Member]
Revenues from External Customers and Long-Lived Assets [Line Items]
Total Gross sales											$ 5,975	$ 8,987	$ 11,234

[1] Income from continuing operations includes a gain on sale of an office building of $4,680 and a corresponding tax expense of $1,470 and a benefit of $1,155 due to changes in tax laws.

[2] Income from continuing operations includes the reversal of a valuation allowance on deferred tax assets of $36,287 and the impact on deferred taxes of a statutory rate change of $1,328.