CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS (USD $) In Thousands, except Per Share data, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Income Statement [Abstract]
Net sales	$ 148,793		$ 101,051		$ 274,019		$ 200,080
Cost of sales	114,140		78,014		213,167		155,678
Gross profit	34,653		23,037		60,852		44,402
Selling, product development and administrative expenses	22,080		13,516		40,653		28,364
Operating income	12,573	[1]	9,521	[1]	20,199	[1]	16,038	[1]
Interest expense	280		76		492		154
Other expense, net	299		18		354		60
Income before income taxes	11,994		9,427		19,353		15,824
Income tax expense	3,754		3,472		7,397		5,377
Net income	$ 8,240		$ 5,955		$ 11,956		$ 10,447
Earnings per share:
Basic (usd per share)	$ 0.50		$ 0.36		$ 0.72		$ 0.63
Diluted (usd per share)	$ 0.49		$ 0.35		$ 0.71		$ 0.62
Weighted average number of common shares outstanding:
Basic (in shares)	16,618		16,612		16,580		16,674
Diluted (in shares)	16,980		16,831		16,925		16,927

[1] Industrial Filtration segment reports results for the period following the date of acquisition of February 20, 2014 through June 30, 2014.