Acquisition of the New Business - Pro Forma Adjustments (Details) - USD ($) $ in Thousands		3 Months Ended			6 Months Ended
	Nov. 02, 2016	Jun. 30, 2017	Dec. 31, 2016	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pro forma results of operations
Amount borrowed					$ 76,456	$ 58,334
First Amended and Restated Credit Agreement | Revolving credit facility
Pro forma results of operations
Amount borrowed	$ 160,000		$ 160,000
Activated Carbon and Filter Aid Business (New Business)
Pro forma results of operations
Net income		$ 5,864		$ 11,811	8,326	15,340
Activated Carbon and Filter Aid Business (New Business) | Incremental deprecation and amortization associated with fair value adjustments to property, plant and equipment and intangible assets, before tax
Pro forma results of operations
Net income				(1,000)		(1,900)
Activated Carbon and Filter Aid Business (New Business) | Incremental interest expense, before tax
Pro forma results of operations
Net income				(1,000)		(2,000)
Activated Carbon and Filter Aid Business (New Business) | Step-up of inventory, before tax
Pro forma results of operations
Net income					600	(2,100)
Activated Carbon and Filter Aid Business (New Business) | Acquisition-related transaction expenses, before tax
Pro forma results of operations
Net income					$ 2,100	(2,100)
Activated Carbon and Filter Aid Business (New Business) | Transaction costs, before tax
Pro forma results of operations
Net income				$ 1,300		$ 2,900