Annual report pursuant to Section 13 and 15(d)

Benefit Plans - Plan Assets (Details)

v3.20.4
Benefit Plans - Plan Assets (Details) - Defined Benefit Pension Plans - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Defined Benefit Plan Disclosure      
Fair value of plan assets $ 362,705 $ 316,721  
Level 1      
Defined Benefit Plan Disclosure      
Fair value of plan assets 184,529 152,681  
Level 2      
Defined Benefit Plan Disclosure      
Fair value of plan assets 172,340 159,326  
Level 3      
Defined Benefit Plan Disclosure      
Fair value of plan assets 5,836 4,714 $ 4,322
Cash and cash equivalents      
Defined Benefit Plan Disclosure      
Fair value of plan assets 787 950  
Cash and cash equivalents | Level 1      
Defined Benefit Plan Disclosure      
Fair value of plan assets 787 950  
Cash and cash equivalents | Level 2      
Defined Benefit Plan Disclosure      
Fair value of plan assets 0 0  
Cash and cash equivalents | Level 3      
Defined Benefit Plan Disclosure      
Fair value of plan assets $ 0 0  
Equity Securities | PQ Corporation Retirement Plan      
Defined Benefit Plan Disclosure      
Target asset plan allocation percentage 45.00%    
Equity Securities | Eco Services Pension Equity Plan      
Defined Benefit Plan Disclosure      
Target asset plan allocation percentage 40.00%    
Equity Securities | Eco Services Hourly Pension Plan      
Defined Benefit Plan Disclosure      
Target asset plan allocation percentage 60.00%    
U.S. investment funds      
Defined Benefit Plan Disclosure      
Fair value of plan assets $ 79,777 67,374  
U.S. investment funds | Level 1      
Defined Benefit Plan Disclosure      
Fair value of plan assets 79,777 67,374  
U.S. investment funds | Level 2      
Defined Benefit Plan Disclosure      
Fair value of plan assets 0 0  
U.S. investment funds | Level 3      
Defined Benefit Plan Disclosure      
Fair value of plan assets 0 0  
International investment funds      
Defined Benefit Plan Disclosure      
Fair value of plan assets 64,986 54,908  
International investment funds | Level 1      
Defined Benefit Plan Disclosure      
Fair value of plan assets 53,792 44,905  
International investment funds | Level 2      
Defined Benefit Plan Disclosure      
Fair value of plan assets 11,194 10,003  
International investment funds | Level 3      
Defined Benefit Plan Disclosure      
Fair value of plan assets $ 0 0  
Fixed income securities | PQ Corporation Retirement Plan      
Defined Benefit Plan Disclosure      
Target asset plan allocation percentage 55.00%    
Fixed income securities | Eco Services Pension Equity Plan      
Defined Benefit Plan Disclosure      
Target asset plan allocation percentage 60.00%    
Fixed income securities | Eco Services Hourly Pension Plan      
Defined Benefit Plan Disclosure      
Target asset plan allocation percentage 40.00%    
Government securities      
Defined Benefit Plan Disclosure      
Fair value of plan assets $ 39,541 31,040  
Government securities | Level 1      
Defined Benefit Plan Disclosure      
Fair value of plan assets 33,505 23,500  
Government securities | Level 2      
Defined Benefit Plan Disclosure      
Fair value of plan assets 6,036 7,540  
Government securities | Level 3      
Defined Benefit Plan Disclosure      
Fair value of plan assets 0 0  
Corporate bonds      
Defined Benefit Plan Disclosure      
Fair value of plan assets 16,771 14,900  
Corporate bonds | Level 1      
Defined Benefit Plan Disclosure      
Fair value of plan assets 16,668 14,782  
Corporate bonds | Level 2      
Defined Benefit Plan Disclosure      
Fair value of plan assets 103 118  
Corporate bonds | Level 3      
Defined Benefit Plan Disclosure      
Fair value of plan assets 0 0  
Investment fund bonds      
Defined Benefit Plan Disclosure      
Fair value of plan assets 112,024 106,198  
Investment fund bonds | Level 1      
Defined Benefit Plan Disclosure      
Fair value of plan assets 0 1,170  
Investment fund bonds | Level 2      
Defined Benefit Plan Disclosure      
Fair value of plan assets 112,024 105,028  
Investment fund bonds | Level 3      
Defined Benefit Plan Disclosure      
Fair value of plan assets 0 0  
Insurance contracts      
Defined Benefit Plan Disclosure      
Fair value of plan assets 48,819 41,351  
Insurance contracts | Level 1      
Defined Benefit Plan Disclosure      
Fair value of plan assets 0 0  
Insurance contracts | Level 2      
Defined Benefit Plan Disclosure      
Fair value of plan assets 42,983 36,637  
Insurance contracts | Level 3      
Defined Benefit Plan Disclosure      
Fair value of plan assets $ 5,836 $ 4,714