Commitment and Contingencies - Additional Information (Detail) - New Jersey [Member] - Class Action [Member] $ in Millions	3 Months Ended
Mar. 31, 2018 USD ($)
Commitment And Contingencies [Line Items]
Settlement agreement, amount	$ 8.0
Settlement agreement, amount after tax	$ 6.0

Amount awarded to other party in judgment or settlement of litigation.

No definition available.

Name:	us-gaap_LitigationSettlementAmountAwardedToOtherParty
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration