Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Dec. 31, 2017
Loss Contingencies [Line Items]
Environmental remediation liabilities - discounted	$ 44,100	$ 28,100
Accrual for environmental loss contingencies - weighted-average discount rate	3.70%	3.60%
Environmental remediation liabilities - undiscounted	$ 85,500	$ 68,200
Legal accrual	17,628
Tax indemnification liability	32,400	$ 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	$ 20,000