General (Details)	Mar. 31, 2013 item
General
Number of natural gas fueling locations	358
Number of states where the natural gas stations are located	32

The number of states the entity operates in as of the balance sheet date.

No definition available.

Name:	us-gaap_NumberOfStatesInWhichEntityOperates
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant