XML 88 R76.htm IDEA: XBRL DOCUMENT v3.21.2
Employee benefit plans (Details) - USD ($)
 3 Months Ended 6 Months Ended
Jun. 30, 2021
Jun. 30, 2020
Jun. 30, 2021
Jun. 30, 2020
Qualified plan | Underfunded plan | Pension benefits        
Defined benefit plan disclosure, net periodic benefit cost [Line Items]        
Service cost $ 0 $ 0 $ 0 $ 0
Interest cost 2,455,000 3,074,000 4,910,000 6,047,000
Expected return on assets (4,894,000) (5,214,000) (9,788,000) (9,975,000)
Amortization of prior service credit 0 0 0 0
Amortization of net actuarial loss 2,004,000 1,723,000 4,008,000 3,586,000
Net periodic benefit credit, including amount capitalized (435,000) (417,000) (870,000) (342,000)
Less amount capitalized 0 0 0 0
Net periodic benefit credit (435,000) (417,000) (870,000) (342,000)
Qualified plan | Overfunded Plan | Other postretirement benefits        
Defined benefit plan disclosure, net periodic benefit cost [Line Items]        
Service cost 400,000 414,000 800,000 766,000
Interest cost 466,000 627,000 932,000 1,218,000
Expected return on assets (1,275,000) (1,401,000) (2,550,000) (2,649,000)
Amortization of prior service credit (349,000) (402,000) (698,000) (699,000)
Amortization of net actuarial loss 6,000 142,000 12,000 144,000
Net periodic benefit credit, including amount capitalized (752,000) (620,000) (1,504,000) (1,220,000)
Less amount capitalized 44,000 35,000 83,000 67,000
Net periodic benefit credit (796,000) (655,000) (1,587,000) (1,287,000)
Nonqualified plan | Unfunded plan | Supplemental employee retirement plans        
Defined benefit plan disclosure, net periodic benefit cost [Line Items]        
Net periodic benefit credit $ 769,000 $ 900,000 $ 1,500,000 $ 1,900,000