Debt - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2015 USD ($)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 EUR (€)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 GBP (£)	Sep. 30, 2014 USD ($)	Sep. 30, 2015 USD ($)	Sep. 30, 2015 CNY (¥)	Sep. 30, 2015 GBP (£)	Sep. 03, 2015 USD ($)	Dec. 31, 2014 EUR (€)	Dec. 31, 2014 USD ($)	Nov. 18, 2014 USD ($)	Aug. 27, 2013 USD ($)	Jul. 31, 2013 USD ($)	Jul. 31, 2013 CNY (¥)	Aug. 17, 2012 EUR (€)	Aug. 17, 2012 USD ($)
Line of Credit Facility [Line Items]
Increased credit facility commitment for either revolving credit facility or term loan facility													$ 50,000,000
Unused credit availability under credit facility							$ 45,700,000					$ 71,500,000
Weighted average interest rate on outstanding borrowings			3.20%				3.20%	3.20%	3.20%		2.24%	2.24%
Maximum consolidated leverage ratio			3.75				3.75	3.75	3.75
Minimum fixed charge coverage ratio			1.25	1.25	1.25
Increased interest rate of loan due to default			2.00%				2.00%	2.00%	2.00%
Other expenses for credit agreement							$ 6,000,000
Payment of customary fees under credit agreement	$ 2,900,000
Unamortized deferred financing costs							4,500,000					$ 2,400,000
Amortization expense	$ 200,000	$ 100,000		$ 400,000		$ 400,000
Total outstanding borrowings							194,283,000					111,856,000
Restricted cash balances							5,350,000					1,200,000
Credit Agreement [Member]
Line of Credit Facility [Line Items]
Debt instrument fees expensed							300,000
United Kingdom [Member] | Debenture Agreement [Member]
Line of Credit Facility [Line Items]
Cash deposit				2,800,000	£ 1,900,000
Germany [Member] | Debenture Agreement [Member]
Line of Credit Facility [Line Items]
Cash deposit			€ 600,000	700,000
Singapore [Member]
Line of Credit Facility [Line Items]
Cash deposit				$ 300,000
Aarding Thermal Acoustics B.V. ("Aarding") [Member]
Line of Credit Facility [Line Items]
Facilities agreement, amount																	€ 10,500,000	$ 11,800,000
Maximum debt as proportion of EBITDA																	3.0	3.0
Federal Funds Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate			0.50%	0.50%	0.50%
One-Month LIBOR [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate			1.00%	1.00%	1.00%
Bank Overdrafts [Member] | Aarding Thermal Acoustics B.V. ("Aarding") [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities			€ 3,300,000				$ 3,700,000				€ 0	0
Weighted average interest rate on outstanding borrowings			1.95%				1.95%	1.95%	1.95%
Facilities agreement, amount																	€ 3,500,000	$ 3,900,000
Debt instrument variable interest rate description			Three months Euribor plus 195 basis points	Three months Euribor plus 195 basis points	Three months Euribor plus 195 basis points
PMFG, Inc. [Member] | PCMC Facility [Member] | Loan Agreement [Member]
Line of Credit Facility [Line Items]
Facilities agreement, amount															$ 6,900,000	¥ 43,000,000
Debt instrument, maturity date			Dec. 20, 2017	Dec. 20, 2017	Dec. 20, 2017
Total outstanding borrowings							$ 4,400,000	¥ 28,000,000
Interest rate			7.00%				7.00%	7.00%	7.00%
Restricted cash balances							$ 400,000
PMFG, Inc. [Member] | PCMC LOC [Member] | Loan Agreement [Member]
Line of Credit Facility [Line Items]
Debt instrument, maturity date			Dec. 31, 2015	Dec. 31, 2015	Dec. 31, 2015
Interest rate			6.50%				6.50%	6.50%	6.50%
Short-term financing with Bank of China Limited							$ 1,600,000	¥ 10,000,000
Term Loan [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities														$ 65,000,000
Increased credit facility commitment for either revolving credit facility or term loan facility										$ 170,000,000			35,000,000
Total outstanding borrowings							170,000,000					90,072,000
Term Loan [Member] | Met-Pro Corporation [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities														65,000,000
U.S. Dollar Revolving Loans [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities														70,500,000
Increased credit facility commitment for either revolving credit facility or term loan facility													$ 15,000,000
Decreased credit facility commitment for either revolving credit facility or term loan facility										$ 60,500,000
U.S. Dollar Revolving Loans [Member] | Met-Pro Corporation [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities														52,000,000
Multi-currency Revolving Credit Facility [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities														$ 19,500,000
Letters of Credit [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities							15,300,000					9,500,000
Bank Guarantees [Member] | Singapore [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities							1,100,000
Bank Guarantees [Member] | Aarding Thermal Acoustics B.V. ("Aarding") [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities			€ 6,200,000				$ 7,000,000				€ 5,500,000	$ 6,700,000
Weighted average interest rate on outstanding borrowings			2.65%				2.65%	2.65%	2.65%
Facilities agreement, amount																	€ 7,000,000	$ 7,900,000
Debt instrument variable interest rate description			Three months Euribor plus 265 basis points	Three months Euribor plus 265 basis points	Three months Euribor plus 265 basis points
Bank Guarantees [Member] | PMFG, Inc. [Member] | PCMC Facility [Member] | Loan Agreement [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities							$ 400,000
Letter Of Credit And Bank Guarantees [Member] | United Kingdom [Member] | Debenture Agreement [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities							9,100,000		£ 6,000,000
Outstanding stand-by letters of credit and bank guarantees				$ 5,400,000	£ 3,600,000
Letter Of Credit And Bank Guarantees [Member] | Germany [Member] | Debenture Agreement [Member]
Line of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities			€ 4,800,000				$ 5,400,000
Outstanding stand-by letters of credit and bank guarantees			€ 1,800,000	$ 2,000,000
Minimum [Member] | Cross Currency Interest Rate Contract [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate			2.00%	2.00%	2.00%
Minimum [Member] | Aarding Thermal Acoustics B.V. ("Aarding") [Member]
Line of Credit Facility [Line Items]
Borrowers solvency ratio																	30.00%	30.00%
Minimum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate			1.00%	1.00%	1.00%
Maximum [Member] | Cross Currency Interest Rate Contract [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate			3.00%	3.00%	3.00%
Maximum [Member] | Base Rate [Member]
Line of Credit Facility [Line Items]
Basis spread on variable rate			2.00%	2.00%	2.00%