Recent Accounting Pronouncements - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2017	Sep. 30, 2017	Jan. 01, 2018
ASU 2017-07 | Cost of Sales
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Reclassification adjustment to other components of net periodic pension and OPEB cost	$ 2.8	$ 8.0
ASU 2017-07 | Selling, General and Administrative Expenses
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Reclassification adjustment to other components of net periodic pension and OPEB cost	$ 1.7	$ 4.8
ASU 2016-01
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Accumulated other comprehensive income related to marketable securities reclassified to beginning retained earnings			$ 4.8