Retirement plans (Tables)

6 Months Ended

Jun. 30, 2020

Retirement Benefits [Abstract]

Benefit Costs

Pension costs, which primarily include costs for the qualified TRP and the non-qualified SERP, are presented in the following table (in thousands):

	Quarter ended June 30,						Six months ended June 30,
	2020			2019			2020			2019
Service cost-benefits earned during the period	$	2		$	—		$	4		$	—
Interest cost on benefit obligation	4,879			5,773			9,737			11,523
Expected return on plan assets	(7,779		)	(6,585		)	(15,529		)	(13,160		)
Amortization of prior service cost	87			20			45			45
Amortization of actuarial loss	1,481			1,541			3,081			3,041
Pension payment timing related charge	—			686			—			686
(Gains from) expense for company-sponsored retirement plans	$	(1,330	)	$	1,435		$	(2,662	)	$	2,135