XML 133 R114.htm IDEA: XBRL DOCUMENT v3.20.4
Employee Benefit Plans: Accumulated Benefit Obligations (Details) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Pension Plan    
Defined Benefit Plan Disclosure [Line Items]    
Defined Benefit Plan, Accumulated Benefit Obligation $ 498,815 $ 470,615
Supplemental Employee Retirement Plan    
Defined Benefit Plan Disclosure [Line Items]    
Defined Benefit Plan, Accumulated Benefit Obligation 54,779 49,241
Other Postretirement Benefits Plan    
Defined Benefit Plan Disclosure [Line Items]    
Defined Benefit Plan, Accumulated Benefit Obligation $ 70,238 $ 65,277