Commitments and Contingencies - Additional Information (Detail) $ in Millions	3 Months Ended
Mar. 31, 2015 USD ($) Vehicle	Jun. 30, 2015 Vehicle
Commitments And Contingencies Disclosure [Abstract]
Purchase contract units, tractors	300
Total costs of purchasing tractors \| $	$ 43.4
Number of tractors received		51

Minimum amount of other commitment not otherwise specified in the taxonomy. Excludes commitments explicitly modeled in the taxonomy, including but not limited to, long-term and short-term purchase commitments, recorded and unrecorded purchase obligations, supply commitments, registration payment arrangements, leases, debt, product warranties, guarantees, environmental remediation obligations, and pensions.

No definition available.

Name:	us-gaap_OtherCommitment
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant