Organization - Additional Information (Detail)	Sep. 30, 2017 ServiceProvider State
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of service providers operated \| ServiceProvider	449
Number of states in which Company operates \| State	27

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