Acquisitions - Additional Information (Detail)	3 Months Ended		6 Months Ended			3 Months Ended	6 Months Ended			3 Months Ended	6 Months Ended	0 Months Ended	3 Months Ended	6 Months Ended	0 Months Ended		3 Months Ended
	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2013 USD ($)	Dec. 31, 2013 USD ($)	Jun. 30, 2013 Aarding Thermal Acoustics B.V. ("Aarding") [Member] USD ($)	Jun. 30, 2014 Aarding Thermal Acoustics B.V. ("Aarding") [Member] USD ($)	Jun. 30, 2014 Aarding Thermal Acoustics B.V. ("Aarding") [Member] EUR (€)	Dec. 31, 2013 Aarding Thermal Acoustics B.V. ("Aarding") [Member] USD ($)	Jun. 30, 2013 Pristine Water Solution [Member] USD ($)	Jun. 30, 2013 Pristine Water Solution [Member] USD ($)	Aug. 27, 2013 Met-Pro [Member] USD ($)	Mar. 31, 2013 Met-Pro [Member] USD ($)	Jun. 30, 2014 Met-Pro [Member] USD ($)	Aug. 27, 2013 Met-Pro [Member] Maximum [Member]	Aug. 27, 2013 Met-Pro [Member] Minimum [Member]	Mar. 31, 2013 Met-Pro [Member] Minimum [Member]
Business Acquisition [Line Items]
Cash paid on acquisition							$ 24,400,000
Company's common stock							763,673
Fair value of common stock issued							6,800,000
Business combination contingent consideration paid							5,500,000	4,000,000
Prepaid compensation recognized in Prepaid expenses and other current assets							1,100,000		1,100,000
Prepaid compensation recognized in Deferred Charges and other assets							2,900,000		3,500,000
Business combination compensation expenses	300,000			300,000		200,000	500,000
Earn out payment upon attainment of specified financial targets through December 31, 2017							7,500,000	5,500,000
Earn out expenses	400,000			500,000		400,000	800,000
Earn out expenses included in accounts payable and accrued expenses							500,000		1,300,000
Cash consideration per share												$ 13.75
Stock consideration per share													$ 13.75
Exchange ratio												1.0843			1.3520	1.0000	1.0000
Percentage of common stock converted into cash														51.60%
Value of shares transferred for cash														104,400,000
Trading day period														15 days
Trading price														$ 12.6814
Shares of common stock in aggregate stock consideration														7,726,235
Percentage of cash consideration														77.56%
Percentage of stock consideration														22.44%
Value of stock recorded														98,000,000
Consideration for cancelling of options and restricted stock units														4,900,000
Proceeds from sale of assets held for sale			6,600,000
Proceeds from sale of assets held for sale, closing balance	4,243,000		4,243,000		11,083,000
Net sales		$ 67,729,000		$ 130,357,000						$ 1,300,000	$ 2,400,000