Employee Benefit Plans Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Pension Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 2,726	$ 3,257	$ 3,053
Expected return on assets	(3,925)	(2,754)	(2,047)
Net amortization and deferral	1,859	1,981	2,429
Net periodic benefit cost	660	2,484	3,435
Other Postretirement Benefit Plans
Defined Benefit Plan Disclosure [Line Items]
Interest cost	43	61	57
Net amortization and deferral	(548)	(556)	(559)
Net periodic benefit cost	$ (505)	$ (495)	$ (502)