Commitments and Contingencies - Additional Information (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Commitments And Contingencies Disclosure [Line Items]
Environmental remediation liabilities- discounted	$ 28.1	$ 22.8
Accrual for environmental loss contingencies- weighted-average discount rate	3.60%	3.50%
Environmental remediation liabilities- undiscounted	$ 68.2	$ 61.1
Potential revision on future environmental remediation costs before tax	18.0
Rental expense	$ 31.2	31.4	$ 34.8
Discontinued operations
Commitments And Contingencies Disclosure [Line Items]
Rental expense		$ 11.8	$ 10.2