Summary of Significant Accounting Policies - Additional Information (Details) - Accounting Standards Update 2017-07 - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017
Selling, General and Administrative Expenses
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic pension and OPEB (income) expense, non-service components	$ (0.3)	$ (0.9)
Other Income, Net
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net periodic pension and OPEB (income) expense, non-service components	$ 0.3	$ 0.9