Revenue from Contracts with Customers - Schedule of Deferred Revenue and Customer Advances by Arrangement (Parenthetical) (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Change in Contract with Customer, Liability [Line Items]
Long-term deferred revenue	$ 5.1	$ 3.3
Deferred revenue and customer advances	30.4		$ 21.5
Deferred Revenue [Member]
Change in Contract with Customer, Liability [Line Items]
Deferred revenue and customer advances	19.7	12.4
Customer Advances [Member]
Change in Contract with Customer, Liability [Line Items]
Deferred revenue and customer advances	$ 10.7	$ 9.1