Inventory - Additional Information (Detail)	Sep. 30, 2016
Minimum [Member]
Inventory [Line Items]
Percentage of vehicles in transit to customers	97.00%

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_InventoryLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration