Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Loss Balance Sheet (Details) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive (Income) Loss, Defined Benefit Plan, after Tax	$ 9,220		$ 8,090
Accumulated Other Comprehensive Income (Loss), Pension and Other Postretirement Benefit Plans Net Unamortized (Gain) Loss, Tax	2,451		$ 4,356
AOCI Attributable to Parent [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Reclassification of excess income tax benefits	$ (1,742)	$ 0