Ecovyst, Inc. Annual report pursuant to Section 13 and 15(d)

Reportable Segments - Sales by Geography (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Revenues from External Customers and Long-Lived Assets
Sales	$ 352,375	$ 423,801	$ 431,675	$ 359,221	$ 380,041	$ 427,203	$ 434,713	$ 366,197	$ 1,567,072	$ 1,608,154	$ 1,472,101
United States
Revenues from External Customers and Long-Lived Assets
Sales									953,511	963,722	874,764
Netherlands
Revenues from External Customers and Long-Lived Assets
Sales									117,211	127,803	118,567
United Kingdom
Revenues from External Customers and Long-Lived Assets
Sales									118,626	119,586	116,410
Other foreign countries
Revenues from External Customers and Long-Lived Assets
Sales									$ 377,724	$ 397,043	$ 362,360