Employee Benefit Plans Summary of Pension Plan and Postretirement Plan Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 681	$ 813	$ 2,043	$ 2,443
Expected return on plan assets	(982)	(688)	(2,946)	(2,066)
Net amortization and deferral	465	496	1,395	1,486
Net periodic benefit	164	621	492	1,863
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	11	15	33	45
Net accretion and deferral	(137)	(139)	(411)	(417)
Net periodic benefit	$ (126)	$ (124)	$ (378)	$ (372)