Commitments and Contingencies - Additional Information (Detail) $ in Millions	Sep. 30, 2018 USD ($)
Commitments And Contingencies Disclosure [Abstract]
Pro rata share of letters of credit outstanding	$ 1.8

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

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