Employee Benefit Plans Summary of Pension Plan and Postretirement Plan Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 681	$ 815	$ 1,362	$ 1,630
Expected return on plan assets	(982)	(689)	(1,964)	(1,378)
Net amortization and deferral	465	495	930	990
Net periodic benefit	164	621	328	1,242
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	11	15	22	30
Net accretion and deferral	(137)	(139)	(274)	(278)
Net periodic benefit	$ (126)	$ (124)	$ (252)	$ (248)