Environmental Environmental (Details) - USD ($)	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Loss Contingencies [Line Items]
Environmental Remediation Expense	$ 0	$ 0
Accrued Environmental Expense	6,400,000		$ 6,500,000
Accrued Environmental Expense, Noncurrent	4,900,000		5,000,000
Affiliated Entity
Loss Contingencies [Line Items]
Accrued Environmental Expense	$ 700,000		$ 800,000