Investments - Additional Information (Detail) $ in Thousands	9 Months Ended
Sep. 30, 2016 USD ($)
Schedule of Available-for-sale Securities [Line Items]
Unrealized net (losses) gains on available-for-sale securities	$ (166)
Municipal Securities [Member]
Schedule of Available-for-sale Securities [Line Items]
Maturity period of investments	One year or less

The change in unrealized holding gain (loss), net of tax, on available-for-sale securities included in a separate component of shareholders' equity during the period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 320
-SubTopic 10
-Section 50
-Paragraph 9
-Subparagraph (d)
-URI http://asc.fasb.org/extlink&oid=73527792&loc=d3e27357-111563

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