Employee Benefit Plans Summary of Pension Plan and Postretirement Plan Net Periodic Benefit Cost (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Pension Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Service cost	$ 0	$ 172	$ 0	$ 516
Interest cost	830	880	2,490	2,640
Expected return on plan assets	(451)	(580)	(1,353)	(1,739)
Net amortization and deferral	663	605	1,989	1,815
Net periodic benefit	1,042	1,077	3,126	3,232
Other Postretirement Benefits Plan [Member]
Defined Benefit Plan Disclosure [Line Items]
Interest cost	17	21	51	64
Expected return on plan assets	0	0	0	(1)
Net accretion and deferral	(141)	(138)	(423)	(413)
Net periodic benefit	$ (124)	$ (117)	$ (372)	$ (350)