Employee Benefits (Net Periodic Benefit Cost) (Details) - Other Postretirement Benefit Plan - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items]
Decrease In Service and Interest Component of Net Periodic Benefit Cost	$ 800
Service cost	2,769	$ 3,454	$ 2,845
Interest cost	3,167	4,035	4,463
Expected return on plan assets	(1,835)	(2,070)	(2,116)
Amortization of:
Prior service benefit	(3,901)	(3,068)	(4,753)
Net gain	(2,374)	(2,025)	(2,671)
Net periodic benefit cost	$ (2,174)	$ 326	$ (2,232)