Acquisition - Fair Values of Assets and Liabilities Assumed at Date of Closing after Company Finalized Purchase Accounting - PMFG (Detail) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015	Dec. 31, 2014
Business Acquisition [Line Items]
Goodwill	$ 224,531	$ 220,163	$ 165,861
PMFG, Inc. [Member]
Business Acquisition [Line Items]
Current assets (including cash of $27,100)	92,293
Property and equipment	24,787
Other assets	953
Assets held for sale	950
Goodwill	59,860
Intangible – finite life	29,940
Intangible – indefinite life	10,280
Total assets acquired	219,063
Current liabilities assumed	(73,364)
Deferred income tax liability	(800)
Long term liabilities assumed	(3,961)
Noncontrolling interest	(4,212)
Net assets acquired	$ 136,726