Quarterly Results of Operations (UNAUDITED) (Results of Operations) (Details) - USD ($) $ / shares in Units, $ in Thousands		3 Months Ended								12 Months Ended
		Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales	[1]									$ 641,443	$ 610,911	$ 537,482
Gross margin										235,362	234,753	188,537
Income (loss) from continuing operations										$ 46,320	$ 53,412	$ 38,203
Net income per share:
Basic income from continuing operations (in dollars per share)										$ 2.52	$ 2.94	$ 2.22
Diluted income from continuing operationss (in dollars per share)										$ 2.48	$ 2.86	$ 2.15
Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales		$ 152,928	$ 160,366	$ 163,098	$ 165,051	$ 147,724	$ 163,052	$ 153,495	$ 146,640
Gross margin		52,604	59,530	60,589	62,355	58,335	64,548	57,138	53,919
Income (loss) from continuing operations		$ 6,577	$ 12,455	$ 13,540	$ 13,627	$ 7,013	$ 20,388	$ 10,902	$ 14,580
Net income per share:
Basic income from continuing operations (in dollars per share)		$ 0.37	$ 0.68	$ 0.73	$ 0.74	$ 0.38	$ 1.12	$ 0.60	$ 0.81
Diluted income from continuing operationss (in dollars per share)		$ 0.37	$ 0.67	$ 0.71	$ 0.72	$ 0.37	$ 1.09	$ 0.58	$ 0.79
Change from LIFO to FIFO
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Net sales		$ 152,928	$ 160,366	$ 163,098	$ 165,051	$ 147,724	$ 163,052	$ 153,495	$ 146,640
Gross margin		52,604	59,672	60,661	62,425	58,695	64,576	57,376	54,107
Income (loss) from continuing operations		$ 6,577	$ 12,546	$ 13,554	$ 13,643	$ 7,247	$ 20,407	$ 11,056	$ 14,702		$ 53,412	$ 38,203
Net income per share:
Basic income from continuing operations (in dollars per share)		$ 0.37	$ 0.68	$ 0.73	$ 0.74	$ 0.40	$ 1.12	$ 0.61	$ 0.82
Diluted income from continuing operationss (in dollars per share)		$ 0.37	$ 0.67	$ 0.71	$ 0.72	$ 0.39	$ 1.09	$ 0.59	$ 0.79
Change from LIFO to FIFO | Scenario, Previously Reported
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Income (loss) from continuing operations											$ 52,883	$ 37,659

[1] Net sales are allocated to countries based on the location of the customer.