Senior Debt - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Mar. 31, 2016	Jun. 30, 2017	Mar. 31, 2019	Dec. 31, 2016	Jul. 31, 2016	Jul. 12, 2016
Line Of Credit Facility [Line Items]
Prepayment of outstanding debt	$ 2,000,000		$ 4,300,000
Credit facility, principal payment remainder of 2017	3,500,000		3,500,000
Credit facility, principal payment 2018	8,500,000		8,500,000
Credit facility, principal payment 2019	10,000,000		10,000,000
Credit facility, principal payment 2020	$ 95,300,000		$ 95,300,000
Weighted average interest rate on outstanding borrowings	3.47%		3.47%		3.26%
Interest rate swap, fair value					$ 200,000
Changes in fair value income (loss)		$ 500,000
Credit agreement, date of amendment			Jun. 09, 2017
Maximum consolidated leverage ratio	325.00%		325.00%
ING Bank N.V. ("Aarding") [Member]
Line Of Credit Facility [Line Items]
Total borrowing capacity	$ 14,900,000		$ 14,900,000		14,900,000
ING Bank N.V. ("Aarding") [Member] | Bank Overdrafts [Member]
Line Of Credit Facility [Line Items]
Total outstanding borrowings under Credit Facility	$ 200,000		$ 200,000		0
Peerless Propulsys [Member]
Line Of Credit Facility [Line Items]
Ownership interest in the equity and earnings							100.00%
Peerless Propulsys [Member] | PMFG, Inc. [Member]
Line Of Credit Facility [Line Items]
Interest rate	1.50%		1.50%
Noncontrolling interest, ownership percentage by parent	60.00%		60.00%
Percentage of ownership by parent in net income loss			80.00%
Promissory note issued in exchange for ownership in equity			$ 5,300,000
Promissory note due date			Jul. 11, 2019
Ownership interest in the equity and earnings	100.00%		100.00%
Notes payable amount outstanding					5,300,000	$ 5,300,000
Debt Instrument, Term			30 days
Notes payable description			The note is payable at the earlier of July 11, 2019 or 30 days subsequent to the sale of building and land that the Company owns in China.
Building and land expected for sale, period			1 year
Scenario Forecast [Member]
Line Of Credit Facility [Line Items]
Maximum consolidated leverage ratio				300.00%
Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Unused credit availability under credit facility	$ 59,300,000		$ 59,300,000		62,000,000
Letters of Credit [Member]
Line Of Credit Facility [Line Items]
Aggregate principal amount outstanding under the credit facilities	20,700,000		20,700,000		18,000,000
Bank Guarantee Facility [Member] | ING Bank N.V. ("Aarding") [Member]
Line Of Credit Facility [Line Items]
Aggregate principal amount outstanding under the bank gaurantee	4,700,000		4,700,000		5,300,000
China Facility [Member]
Line Of Credit Facility [Line Items]
Total borrowing capacity	$ 4,400,000		$ 4,400,000		$ 4,300,000
Interest rate					4.79%
China Facility [Member] | US Dollar Borrowings [Member]
Line Of Credit Facility [Line Items]
Total outstanding borrowings under Credit Facility					$ 1,296,000