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, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Revenues from External Customers and Long-Lived Assets
Sales	$ 380,041	$ 427,203	$ 434,713	$ 366,197	$ 358,074	$ 391,829	$ 389,267	$ 332,931	$ 1,608,154	$ 1,472,101	$ 1,064,177
United States
Revenues from External Customers and Long-Lived Assets
Sales									963,722	874,764	705,348
Netherlands
Revenues from External Customers and Long-Lived Assets
Sales									127,803	118,567	79,821
United Kingdom
Revenues from External Customers and Long-Lived Assets
Sales									119,586	116,410	67,494
Other foreign countries
Revenues from External Customers and Long-Lived Assets
Sales									$ 397,043	$ 362,360	$ 211,514