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, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 194	$ 0	$ 344
Interest cost	830	879	1,660	1,760
Expected return on plan assets	(451)	(433)	(902)	(1,159)
Net amortization and deferral	663	428	1,326	1,210
Net periodic benefit	1,042	1,068	2,084	2,155
Other Postretirement Benefit Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	17	5	34	43
Expected return on plan assets	0	(1)	0	(1)
Net accretion and deferral	(141)	(210)	(282)	(275)
Net periodic benefit	$ (124)	$ (206)	$ (248)	$ (233)