Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2016	Dec. 31, 2015
Commitments And Contingencies Disclosure [Line Items]
Environmental remediation liabilities - discounted	$ 25.0	$ 24.5
Environmental remediation liabilities - undiscounted	65.1	$ 64.5
Potential revision on future environmental remediation costs before tax	$ 15.0
Minimum
Commitments And Contingencies Disclosure [Line Items]
Accrual for environmental loss contingencies - discount rate	2.80%
Maximum
Commitments And Contingencies Disclosure [Line Items]
Accrual for environmental loss contingencies - discount rate	4.30%