Employee Benefit Plans Summary of Pension Plan and Postretirement Plan Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 150	$ 145
Interest cost	881	851
Expected return on plan assets	(726)	(752)
Net amortization and deferral	782	782
Net periodic benefit cost	1,087	1,026
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	38	52
Net accretion and deferral	(65)	(65)
Net periodic benefit cost	$ (27)	$ (13)