Pre- and Post-Modification Recorded Investment Balances by Portfolio Class (Detail) (Financial Services, USD $) In Millions, unless otherwise specified	Mar. 31, 2013	Mar. 31, 2012
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment	$ 4.7	$ 12.9
Post-Modification Recorded Investment	4.6	12.2
Retail | Fleet
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment	4.2	11.9
Post-Modification Recorded Investment	4.1	11.2
Retail | Owner/Operator
Financing Receivable, Modifications [Line Items]
Pre-Modification Recorded Investment	0.5	1.0
Post-Modification Recorded Investment	$ 0.5	$ 1.0