Retirement Plans (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Company's pension costs
Pension payment timing related charge		$ 6,300
Retirement Plans
Company's pension costs
Interest cost on benefit obligation	$ 5,750	5,150
Expected return on plan assets	(6,575)	(7,450)
Amortization of prior service cost	25	50
Amortization of actuarial loss	1,500	1,250
Pension payment timing related charge	0	6,300
Expense for company-sponsored retirement plans	$ 700	$ 5,300