Employee Benefits (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Pension Plan
Net periodic benefit cost
Service cost	$ 2,707	$ 1,997
Interest cost	2,066	2,080
Expected return on plan assets	(3,385)	(2,696)
Amortization of prior service credit	0	0
Amortization of net loss	979	901
Net periodic benefit cost	2,367	2,282
Estimated 2020 pension plan contribution, disclosed in prior year 10K			$ 10,000
Contribution by employer	2,500
Postretirement Benefit Plan
Net periodic benefit cost
Service cost	432	456
Interest cost	253	319
Expected return on plan assets	0	0
Amortization of prior service credit	(2,021)	(2,021)
Amortization of net loss	94	223
Net periodic benefit cost	$ (1,242)	$ (1,023)