Ecovyst, Inc. Quarterly report pursuant to Section 13 or 15(d)

Financial Instruments - Effect on Other Comprehensive Income (Details) - Cash Flow Hedging - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Amount of gain (loss) recognized in OCI on derivatives (effective portion)
Amount of gain (loss) recognized in OCI on derivatives (effective portion)	$ (1,870)	$ (94)	$ (5,499)	$ (1,511)
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	107	418	126	1,146
Interest rate caps \| Interest expense
Amount of gain (loss) recognized in OCI on derivatives (effective portion)
Amount of gain (loss) recognized in OCI on derivatives (effective portion)	(1,842)	212	(4,712)	212
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	13	(2)	22	(2)
Natural gas swaps \| Cost of goods sold
Amount of gain (loss) recognized in OCI on derivatives (effective portion)
Amount of gain (loss) recognized in OCI on derivatives (effective portion)	(28)	(306)	(787)	(1,723)
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)
Amount of gain (loss) reclassified from accumulated OCI into income (effective portion)	$ 94	$ 420	$ 104	$ 1,148