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, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	$ 815	$ 696	$ 1,630	$ 1,527
Expected return on plan assets	(689)	(573)	(1,378)	(1,024)
Net amortization and deferral	495	551	990	1,215
Net periodic benefit	621	674	1,242	1,718
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	15	12	30	29
Net accretion and deferral	(139)	(139)	(278)	(280)
Net periodic benefit	$ (124)	$ (127)	$ (248)	$ (251)