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

Benefit Plans - Plan Assets (Details)

Benefit Plans - Plan Assets (Details) $ in Thousands	Dec. 31, 2022 USD ($) plan	Dec. 31, 2021 USD ($)
Defined Benefit Plan Disclosure
Number Of Defined Benefit Pension Plans \| plan	2
Defined Benefit Pension Plans
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 60,629	$ 82,914
Defined Benefit Pension Plans \| Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	60,629	82,914
Defined Benefit Pension Plans \| Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| Cash and cash equivalents
Defined Benefit Plan Disclosure
Fair value of plan assets	244	202
Defined Benefit Pension Plans \| Cash and cash equivalents \| Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	244	202
Defined Benefit Pension Plans \| Cash and cash equivalents \| Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| Cash and cash equivalents \| Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0	0
Defined Benefit Pension Plans \| Equity Securities \| Ecoservices Pension Equity Plan
Defined Benefit Plan Disclosure
Target asset plan allocation percentage	35.00%
Defined Benefit Pension Plans \| Equity Securities \| Ecoservices Hourly Pension Plan
Defined Benefit Plan Disclosure
Target asset plan allocation percentage	30.00%
Defined Benefit Pension Plans \| U.S. investment funds
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 11,435	12,150
Defined Benefit Pension Plans \| U.S. investment funds \| Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	11,435	12,150
Defined Benefit Pension Plans \| U.S. investment funds \| Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| U.S. investment funds \| Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| International investment funds
Defined Benefit Plan Disclosure
Fair value of plan assets	7,803	7,816
Defined Benefit Pension Plans \| International investment funds \| Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	7,803	7,816
Defined Benefit Pension Plans \| International investment funds \| Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| International investment funds \| Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0	0
Defined Benefit Pension Plans \| Fixed income securities \| Ecoservices Pension Equity Plan
Defined Benefit Plan Disclosure
Target asset plan allocation percentage	65.00%
Defined Benefit Pension Plans \| Fixed income securities \| Ecoservices Hourly Pension Plan
Defined Benefit Plan Disclosure
Target asset plan allocation percentage	70.00%
Defined Benefit Pension Plans \| Government securities
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 16,209	28,869
Defined Benefit Pension Plans \| Government securities \| Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	16,209	28,869
Defined Benefit Pension Plans \| Government securities \| Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| Government securities \| Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| Corporate bonds
Defined Benefit Plan Disclosure
Fair value of plan assets	24,938	33,877
Defined Benefit Pension Plans \| Corporate bonds \| Level 1
Defined Benefit Plan Disclosure
Fair value of plan assets	24,938	33,877
Defined Benefit Pension Plans \| Corporate bonds \| Level 2
Defined Benefit Plan Disclosure
Fair value of plan assets	0	0
Defined Benefit Pension Plans \| Corporate bonds \| Level 3
Defined Benefit Plan Disclosure
Fair value of plan assets	$ 0	$ 0