Pension and Other Postretirement Benefit Plans Components of Net Periodic Pension Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Pension and Other Postretirement Benefit Plans [Abstract]
Defined Benefit Plan, Service Cost	$ 1,456	$ 1,787	$ 1,445
Defined Benefit Plan, Interest Cost	1,329	1,192	1,756
Defined Benefit Plan, Expected Return on Plan Assets	(1,117)	(986)	(1,303)
Defined Benefit Plan, Amortization of Transition Obligations (Assets)	0	(96)	(87)
Defined Benefit Plan, Amortization of Prior Service Cost (Credit)	(81)	(85)	7
Defined Benefit Plan, Amortization of Gains (Losses)	593	727	540
Defined Benefit Plan, Net Periodic Benefit Cost	$ 2,180	$ 2,539	$ 2,358