Pension and Employee Benefit Plans - Additional Information (Detail) (USD $)	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013 Plans	Dec. 31, 2012
Defined Benefit Plan Disclosure [Line Items]
Number Of Defined Benefit Pension Plans, acquired		2
Increase (decrease) in minimum liability after tax of defined benefit plans	$ 4,000,000	$ 1,400,000	$ 21,000.0
Current Assets Mix percentage	100.00%	100.00%
Assumed average annual returns	7.50%	7.50%	7.50%
Net periodic benefit cost	(141,000)	301,000	342,000
Listing under plans Forms 5500 as providing more than 5% contribution	false
Liability has been provided in the accompanying consolidated financial statements	0
Amounts charged to pension expense	800,000	1,600,000	1,800,000
Employer Matching Contribution on First one percent in 2012 & 2013 and three percent in 2014		100.00%
Employer Matching Contribution on Next Five percent in 2012 & 2013 and three percent in 2014		50.00%
Employer Matching Contribution per employee on Next percentage		5.00%
Employer Maximum Matching Contribution Percent Of Employee Salary Deferral		3.50%
Aggregate matching contributions and discretionary contributions Amount		400,000	400,000
Maximum [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Current Assets Mix percentage	70.00%
Assumed average annual returns	12.00%
Maximum [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Current Assets Mix percentage	40.00%
Assumed average annual returns	6.00%
Minimum [Member] | Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Current Assets Mix percentage	60.00%
Assumed average annual returns	8.00%
Minimum [Member] | Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Current Assets Mix percentage	30.00%
Assumed average annual returns	4.00%
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss for the defined benefit pension plan to be amortized in next year	200,000
Prior service cost for the defined benefit pension plan to be amortized in next year	0
Estimated pension plan cash obligations payable in 2015	1,700,000
Estimated pension plan cash obligations payable in 2016	1,800,000
Estimated pension plan cash obligations payable in 2017	1,800,000
Estimated pension plan cash obligations payable in 2018	1,900,000
Estimated pension plan cash obligations payable in 2019	2,000,000
Estimated pension plan cash obligations payable in 2020 through 2023	10,900,000
Health Care Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Net loss for the defined benefit pension plan to be amortized in next year	(3,000)
Prior service cost for the defined benefit pension plan to be amortized in next year	9,000
Weighted average discount rate to determine the net periodic benefit cost	4.50%	3.75%	4.25%
Net periodic benefit cost	0	(11,000)	(3,000)
Estimated pension plan cash obligations payable in 2015	25,000
Estimated pension plan cash obligations payable in 2016	23,000
Estimated pension plan cash obligations payable in 2017	21,000
Estimated pension plan cash obligations payable in 2018	18,000
Estimated pension plan cash obligations payable in 2019	16,000
Estimated pension plan cash obligations payable in 2020 through 2023	54,000
Employee Deferral Category One [Member]
Defined Benefit Plan Disclosure [Line Items]
Profit sharing and 401(k) savings retirement plan for non-union employees Description	The plan covers substantially all employees who have 30 days of service, and who have attained 18 years of age.
Description Increase in matching contributions	We increased, effective January 1, 2008, the matching contributions to 100% of the first 1% and 50% of the next 5% of the employee deferral for a maximum match of 3.5%.
Employer Matching Contribution on First one percent in 2012 & 2013 and three percent in 2014	100.00%
Employer Matching Contribution on Next Five percent in 2012 & 2013 and three percent in 2014	50.00%
Employer Matching Contribution per employee on Next percentage	5.00%
Employer Maximum Matching Contribution Percent Of Employee Salary Deferral	3.50%
Percentage of Employee salary deferral provision	100.00%
Aggregate matching contributions and discretionary contributions Amount	1,100,000
Employee Deferral Category Two [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Matching Contribution on First one percent in 2012 & 2013 and three percent in 2014	100.00%
Employer Matching Contribution on Next Five percent in 2012 & 2013 and three percent in 2014	50.00%
Employer Matching Contribution per employee on Next percentage	3.00%
Employer Maximum Matching Contribution Percent Of Employee Salary Deferral	4.50%
Yellow Zone [Member]
Defined Benefit Plan Disclosure [Line Items]
Plans Funded Status Description	Between 65 and less than 80 percent
Red Zone [Member]
Defined Benefit Plan Disclosure [Line Items]
Plans Funded Status Description	Less than 65 percent
Green Zone [Member]
Defined Benefit Plan Disclosure [Line Items]
Plans Funded Status Description	At least 80 percent
Met-Pro Technologies LLC ("Met-Pro") [Member]
Defined Benefit Plan Disclosure [Line Items]
Employer Matching Contribution on First one percent in 2012 & 2013 and three percent in 2014	4.00%
Employees contribution to profit sharing plan	25.00%
Employer Matching Contribution	50.00%
Total cash contribution by employer	$ 200,000
Met-Pro Technologies LLC ("Met-Pro") [Member] | Maximum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of employer discretionary contribution	4.00%
Met-Pro Technologies LLC ("Met-Pro") [Member] | Minimum [Member]
Defined Benefit Plan Disclosure [Line Items]
Percentage of employer discretionary contribution	2.00%