Contingencies (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2012
Site Contingency [Line Items]
Proceeds from Legal Settlements		$ 110,000
Recovery of Direct Costs	$ 37,000
Huntsville Site [Member]
Site Contingency [Line Items]
Environmental Remediation Expense To Date	6,200
Additional Expected Project Expenditures Low Estimate	4,200
Additional Expected Project Expenditures High Estimate	10,000
Groundwater Removal [Member] | Norco Site [Member]
Site Contingency [Line Items]
Environmental Remediation Expense To Date	69,300
Additional Expected Project Expenditures Low Estimate	12,500
Additional Expected Project Expenditures High Estimate	$ 23,200