Guarantees and Contingencies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended
Mar. 31, 2014
Commitments And Contingencies Disclosure [Abstract]
Litigation settlement for MTBE	$ 35

Amount of judgment or settlement awarded to (against) the entity in respect of litigation.

No definition available.

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