Pension and Employee Benefit Plans - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2013 Plan
Defined Benefit And Contribution Plan Disclosure [Line Items]
Number Of Defined Benefit Pension Plans, acquired | Plan				2
Increase (decrease) in minimum liability after tax of defined benefit plans	$ 100,000	$ (300,000)	$ 4,000,000
Current Assets Mix percentage	100.00%	100.00%
Assumed average annual returns	7.50%	7.50%	7.50%
Defined benefit plan change in discount rate projected benefit obligation	$ 1,000,000
Annual pension expense	6,000
Defined benefit plan, expected return on plan assets	60,000
Net periodic benefit cost	$ 256,000	$ (106,000)	$ (141,000)
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	2,100,000	1,300,000	1,200,000
Aggregate matching contributions and discretionary contributions Amount	$ 1,500,000	1,200,000	1,100,000
PMFG, Inc. [Member]
Defined Benefit And Contribution Plan Disclosure [Line Items]
Total cash contribution by employer		100,000
Employee Deferral Category One [Member]
Defined Benefit And Contribution 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.
Percentage of Employee salary deferral provision	100.00%
Yellow Zone
Defined Benefit And Contribution Plan Disclosure [Line Items]
Plans Funded Status Description	Between 65 and less than 80 percent
Red Zone
Defined Benefit And Contribution Plan Disclosure [Line Items]
Plans Funded Status Description	Less than 65 percent
Green Zone
Defined Benefit And Contribution Plan Disclosure [Line Items]
Plans Funded Status Description	At least 80 percent
Pension Plan [Member]
Defined Benefit And Contribution 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	3,000
Estimated pension plan cash obligations payable in 2017	1,900,000
Estimated pension plan cash obligations payable in 2018	1,900,000
Estimated pension plan cash obligations payable in 2019	2,100,000
Estimated pension plan cash obligations payable in 2020	2,100,000
Estimated pension plan cash obligations payable in 2021	2,100,000
Estimated pension plan cash obligations payable in 2022 through 2026	10,700,000
Health Care Plan [Member]
Defined Benefit And Contribution Plan Disclosure [Line Items]
Net loss for the defined benefit pension plan to be amortized in next year	0
Prior service cost for the defined benefit pension plan to be amortized in next year	11,000
Net periodic benefit cost	$ 15,000	$ 12,000	$ 0
Weighted average discount rate to determine the net periodic benefit cost	3.00%	3.75%	4.50%
Estimated pension plan cash obligations payable in 2017	$ 25,000
Estimated pension plan cash obligations payable in 2018	22,000
Estimated pension plan cash obligations payable in 2019	19,000
Estimated pension plan cash obligations payable in 2020	16,000
Estimated pension plan cash obligations payable in 2021	13,000
Estimated pension plan cash obligations payable in 2022 through 2026	$ 38,000
Minimum [Member] | Debt Securities [Member]
Defined Benefit And Contribution Plan Disclosure [Line Items]
Current Assets Mix percentage	30.00%
Assumed average annual returns	4.00%
Minimum [Member] | Equity Securities [Member]
Defined Benefit And Contribution Plan Disclosure [Line Items]
Current Assets Mix percentage	60.00%
Assumed average annual returns	8.00%
Maximum [Member] | Debt Securities [Member]
Defined Benefit And Contribution Plan Disclosure [Line Items]
Current Assets Mix percentage	40.00%
Assumed average annual returns	6.00%
Maximum [Member] | Equity Securities [Member]
Defined Benefit And Contribution Plan Disclosure [Line Items]
Current Assets Mix percentage	70.00%
Assumed average annual returns	12.00%