Employee Benefit Plans Summary of Pension Plan and Postretirement Plan Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 815	$ 831
Expected return on plan assets	(689)	(451)
Net amortization and deferral	495	664
Net periodic benefit	621	1,044
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	15	17
Net accretion and deferral	(139)	(141)
Net periodic benefit	$ (124)	$ (124)