Summary of Cumulative Effect of the Changes Made for the Adoption of ASU 2016-13 (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Retained earnings	$ 10,953.6		$ 10,398.5	[1]
Financial Services
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Finance and other receivables, net	11,324.5	$ 12,079.8	12,086.0	[1]
Other assets	844.9	715.1	715.0	[1]
Deferred taxes and other liabilities	$ 791.3	788.7	790.2	[1]
Retained earnings		10,393.9	$ 10,398.5
ASU 2016-13 | Financial Services | Adjustments
New Accounting Pronouncements Or Change In Accounting Principle [Line Items]
Finance and other receivables, net		(6.2)
Other assets		0.1
Deferred taxes and other liabilities		(1.5)
Retained earnings		$ (4.6)

[1] The December 31, 2019 consolidated balance sheet has been derived from audited financial statements.