Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2018	Sep. 30, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Environmental remediation liabilities - discounted	$ 42,800	$ 42,800	$ 28,100
Accrual for environmental loss contingencies - weighted-average discount rate	3.70%	3.70%	3.60%
Environmental remediation liabilities - undiscounted	$ 85,000	$ 85,000	$ 68,200
Legal accrual	(1,017)	27,027
Tax indemnification liability	$ 27,000	27,000	$ 42,700
Minimum
Loss Contingencies [Line Items]
Potential revision on future environmental remediation costs before tax		10,000
Maximum
Loss Contingencies [Line Items]
Potential revision on future environmental remediation costs before tax		25,000
2014 Sales Contract
Loss Contingencies [Line Items]
Legal accrual		16,200
Guarantee From Previously Disposed Business
Loss Contingencies [Line Items]
Legal accrual		$ 10,800