Employee Benefit Plans (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Components of Net Period Benefit Cost
Service cost	$ 2,667,000	$ 2,096,000
Other cost:
Interest cost	4,970,000	5,608,000
Expected return on plan assets	(6,286,000)	(5,483,000)
Recognized net actuarial loss	978,000	887,000
Total other components of the net periodic benefit cost	(338,000)	1,012,000
Net periodic benefit cost	2,329,000	3,108,000
Contribution to defined benefit and other postretirement plans	$ 1,900,000	$ 0