Legal Proceedings, Contingencies and Risks - Additional Information (Detail)	12 Months Ended
Dec. 31, 2016 USD ($)
Minimum [Member]
Loss Contingencies [Line Items]
Claim amount per occurrence	$ 0
Maximum [Member]
Loss Contingencies [Line Items]
Claim amount per occurrence	$ 2,000

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

No definition available.

Name:	us-gaap_LossContingenciesLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration